Best Pilates Between the Knees Ball for 2026: Top Picks Ranked

A pilates between the knees ball is the small soft mini ball, usually 18cm to 25cm, that you squeeze between your knees or thighs to wake up the inner-thigh muscles, the deep core, and the glute med. This guide ranks the best UK options for 2026 across price, firmness and durability, then walks you through a six-move routine you can run at home. It is built for UK home pilates users, pregnancy and postnatal returners, and qualified instructors restocking studio kit.

TL;DR

• "Pilates between the knees ball" almost always means an inflatable soft mini ball, 18cm to 25cm, used for adductor (inner-thigh) and pelvic-floor work.
• Smaller balls (18cm to 20cm) suit knee squeezes and tight upper-thigh cueing. Larger balls (23cm to 25cm) sit better between the thighs and add hip-articulation drills.
• Top pick for UK buyers is the flexa.fit Pilates Ball (18cm): anti-burst, PVC, easy to inflate to taste, free UK delivery with code MEGLIO10.
• Honest competitor picks below: Yogi Bare, Yogamatters, Decathlon Domyos, Manduka, Bala. Each is fine, but most UK buyers do not need to spend more than £15.
• Six starter moves: clamshell with ball, glute bridge with ball squeeze, dead bug with ball, side-lying inner thigh lift, supine spinal articulation, table-top hold.
• For UK home delivery use code MEGLIO10 on flexa.fit. Free UK delivery, no minimum spend.

What is a pilates between the knees ball

It is the soft inflatable mini ball that lives between your knees, thighs or ankles in mat pilates classes. In UK studios you will hear it called a soft ball, a mini ball, an over ball, a pilates squishy or just "the squeeze ball". The shop name varies: pilates soft ball, pilates mini ball, pilates fitness ball, pilates over ball. They are all the same kit.

It is not the big 55cm to 75cm gym ball, and it is not the rigid pilates ring (also called a magic circle). The mini ball deforms when you squeeze it, which is the whole point: the soft give gives your inner thighs and pelvic floor something to press into so the muscles fire harder than they would in mid-air.

The Pilates Foundation, the main UK professional body for the discipline, lists the small ball as one of the core mat props for exactly this reason. It is the cheapest piece of kit in the studio, but for adductor and deep-core cueing it is the most-used one.

Why size and firmness matter

The diameter changes what the ball is good for. Smaller balls keep your knees close together so the squeeze travels into the upper inner thigh and the pelvic floor. Bigger balls open the hips slightly and let you train more like a Reformer short-box pattern, where the ball is between the thighs and the hips have to articulate around it.

Ball size	Best for	Typical user
18cm to 20cm	Knee squeezes, clamshells, pelvic-floor cueing, lumbar support	Most UK home users, postnatal returners, classical mat pilates
22cm to 25cm	Thigh squeezes, glute bridge variants, hip articulation drills	Taller users (5'9"+), instructors running progressive classes
Half-deflated 18cm	Lumbar pillow under spine for bridge and articulation	Anyone with low-back sensitivity, pregnancy returners

Firmness is set by how much you inflate the ball, not by what you buy. Most UK studios inflate to roughly two-thirds full so the ball stays soft enough to compress but firm enough to give feedback. A ball pumped rock-hard turns the squeeze into a bone-on-plastic press and removes most of the inner-thigh work. If you are unsure, see our guide to choosing a pilates ball, which covers size, valve type and inflation in detail.

How we ranked the best pilates between the knees ball options

We tested or cross-checked seven of the most-bought UK pilates mini balls against five criteria: size accuracy versus the advertised diameter, anti-burst PVC quality, valve plug fit, ease of inflation, and value for money. Studio teachers were asked which they would actually order for a class of 12. Where a brand is not stocked in the UK at all we have left it out, even where it ranks well overseas.

1. flexa.fit Pilates Ball (18cm): best pilates between the knees ball overall

The flexa.fit Pilates Ball is an 18cm anti-burst PVC mini ball, sold with a removable plug and a small straw for inflation. It hits the size sweet spot for UK home users: small enough to keep the knees stacked in clamshell and inner-thigh work, but big enough to deflate down to a lumbar pillow for bridge and articulation drills.

Firmness is the win here. The PVC has enough give that you can pump it to taste and still get a smooth compression, rather than the rubbery snap you get on cheaper supermarket balls. Cleaning is straightforward: a damp cloth, mild soap, and it is good for another session. Studio teachers we spoke to said it survives back-to-back classes without the plug working loose.

Pros

• True 18cm at full inflation, the size most UK mat classes use.
• Anti-burst PVC with a secure plug, no slow leaks across a session.
• Deflates down cleanly for a lumbar pillow or travel stowage.
• UK-priced under £12, free UK delivery with no minimum spend.
• Latex-free, so safe for studios training mixed groups including latex-allergic clients.

Cons

• Single size (18cm). Taller users training Reformer-style thigh work may want a 22cm to 25cm option, which flexa.fit does not currently stock.
• Sold solo, no carry bag. If you are kitting a studio out, pair it with a mesh bag for class transport.

Verdict

• Best for: UK home pilates users, postnatal returners, instructors running mat-based group classes.
• Price: under £12.
• Buy from: flexa.fit/products/pilates-ball. Use code MEGLIO10. Free UK delivery, no minimum spend.

Shop the Pilates Ball

2. Yogi Bare Pilates Soft Ball: best premium UK alternative

Yogi Bare is the well-known UK yoga brand and their pilates soft ball sits in the mid-price tier. The ball is a 23cm to 25cm size depending on inflation, which makes it a thigh-squeeze ball rather than a knee-squeeze ball. The brand styling is good, the PVC quality is solid, and you are paying a premium for the brand rather than for anything fundamentally different in the kit.

Pros

• Larger 23cm to 25cm size, useful for taller users and Reformer-style thigh work.
• Strong brand reputation for studio-friendly props.
• Stocked in the UK with quick domestic delivery.

Cons

• Pricier than the flexa.fit equivalent for similar PVC build.
• Larger diameter is wrong for tight inner-thigh and clamshell cueing.

Verdict: Worth it if you specifically want a 23cm to 25cm ball and you like the brand presentation. For most UK buyers looking for an everyday between-the-knees ball, the smaller flexa.fit option is the more useful tool.

3. Yogamatters Pilates Soft Ball: solid mid-range studio pick

Yogamatters is a long-running UK yoga retailer and their own-brand pilates soft ball is a 23cm option that turns up in a lot of studios. It is well made, easy to inflate, and the plug seats firmly. The trade-off is the same as Yogi Bare: at 23cm it is a thigh-squeeze ball, not the more flexible 18cm size that lives between the knees as well as the thighs.

Pros

• Reliable UK stockist with studio-friendly bulk-buy options.
• Good plug fit, no slow leaks.

Cons

• 23cm size limits its use for tight knee squeezes and clamshells.
• Often priced above £10 once you add delivery.

Verdict: A safe pick if you already buy from Yogamatters and want a single-brand studio order. Not the best between-the-knees ball if you train clamshells, hundreds or pelvic-floor cued work.

4. Decathlon Domyos Small Soft Pilates Ball: best budget option

Decathlon's Domyos own-brand small pilates ball is the cheapest credible UK option, usually under £6. It is a 22cm ball, PVC, with the standard removable plug. Build quality is fine for low-frequency home use, and you can pick it up in store if you live near a Decathlon, which solves the delivery question for last-minute buys.

Pros

• Cheapest credible UK pick, often under £6.
• Available in store, useful if you need it the same day.

Cons

• PVC is thinner than flexa.fit or Yogi Bare, plug can work loose over time.
• 22cm size again leans thigh rather than knee squeeze.
• Not always in stock; UK warehousing varies by season.

Verdict: A fine starter ball if you are testing whether you will use one at all. If you train regularly, plan to upgrade within six months.

5. Manduka Mini Ball: premium overseas brand, watch the price

Manduka is the US yoga brand best known for its premium mats, and the Manduka mini ball is a 23cm PVC ball with the brand's usual quiet, studio-grade finish. UK availability is patchy through third-party stockists and the landed price is typically £20 to £25 once delivery is added.

Pros

• Excellent finish quality, popular with private studio teachers.
• Larger size suits thigh work and supine bridge variants.

Cons

• Materially more expensive than UK equivalents for similar PVC build.
• Inconsistent UK stock through resellers.

Verdict: A nice-to-have if you already buy Manduka mats and want a matched aesthetic for your home setup. Otherwise overspending on a piece of kit that is functionally the same as a £10 UK alternative.

6. Pilates Mad Soft Over Ball: classic studio staple

Pilates Mad is the UK distributor most often seen in NHS rehab and private clinic settings, and their soft over ball is the classic 23cm to 25cm pilates squishy. Quality is good, the brand is well known to clinicians, and the price sits between Yogi Bare and Decathlon. We have covered the brand in depth in our Pilates Mad soft ball alternatives review.

Pros

• Trusted in UK clinical and rehab settings.
• Reliable build, plug seats well.

Cons

• Same 23cm to 25cm size limitation as the other mid-tier balls.
• Branding can be hard to match across a multi-ball studio order.

Verdict: A solid clinic-grade pick. Not different enough from the flexa.fit ball to justify the extra spend for a home user.

7. Bala Mini Ball: aesthetic-first, function-second

US lifestyle-fitness brand Bala sells a small pilates ball in their signature pastel colourways. UK availability is via international shipping or selected resellers. The kit looks beautiful on Instagram but is functionally identical to a £10 UK PVC ball.

Pros

• Distinctive colourways for content creators and home aesthetic.
• Good build quality.

Cons

• Overseas brand, UK landed price is typically £25+.
• Function is the same as much cheaper UK equivalents.

Verdict: Buy if you genuinely care about the aesthetic. Skip if you just want a ball that works.

How to choose your pilates between the knees ball

For most UK buyers the decision tree is short. If you train mat pilates at home, want to do clamshells, hundreds and inner-thigh squeezes, and you need one ball that also deflates to a lumbar pillow, buy an 18cm soft ball. If you are taller than 5'9", train Reformer-style thigh squeezes, or want to add a glute-bridge ball-between-thighs progression, go for a 22cm to 25cm option. Either way, pick anti-burst PVC, latex-free, with a removable plug.

Avoid: rigid foam balls, weighted pilates balls (those are a different tool, see our pilates weighted ball guide), and any ball that does not state its inflated diameter on the spec sheet.

A 6-move routine using your pilates between the knees ball

Run this twice through with the ball at two-thirds inflation. Move slowly, breathe out on the squeeze. Stop if anything pinches in the lower back or front of the hip. None of these moves should hurt.

1. Clamshell with ball between knees

Lie on your side, knees stacked and bent to 45 degrees, ball gently held between the knees. Keeping your feet together and the ball trapped, lift your top knee a few inches against the ball's resistance. The ball stops your hips rolling backwards, so the work stays in the glute med rather than leaking into the lower back. 12 reps per side.

2. Glute bridge with ball squeeze

Lie on your back, knees bent, feet flat hip-width, ball between the knees. Squeeze the ball lightly. Press into your heels and lift your hips into a bridge. The ball stops your knees splaying out, which forces the adductors and glute med to share the load with the glute max. 12 reps.

3. Dead bug with ball squeeze

Lie on your back, knees over hips at 90 degrees, ball between the knees. Reach your arms straight up to the ceiling. Maintain the ball squeeze throughout. Slowly lower one arm overhead and the opposite leg out long, then return. The ball squeeze keeps the deep core engaged and stops the lower back arching off the mat. 8 reps per side.

4. Side-lying inner thigh lift with ball

Lie on your side, bottom leg long, top knee bent and resting on the floor in front of you with the ball under that knee. Lift the bottom leg up into the ball, squeezing into it gently. This is the cleanest adductor isolation in pilates. 12 reps per side.

5. Supine spinal articulation over the ball

Half-deflate the ball so it is roughly the size of a small cushion. Place it under your sacrum and let your knees fall in. The ball gives a gentle lumbar support so you can roll the pelvis through a small spinal articulation without compressing the low back. 8 to 10 slow rolls.

6. Table-top hold with ball squeeze

Lie on your back, knees over hips at 90 degrees, ball between the knees. Squeeze and hold. The squeeze closes the lower-abdominal sling and gives a long isometric for the transverse abdominis. Hold for 30 seconds, twice.

For a longer beginner sequence with the same ball, see our beginner pilates ball exercises at home guide.

Pilates between the knees ball: care and lifespan

Inflate to two-thirds, not full. Store away from radiators and direct sunlight. Wipe clean with a damp cloth and mild soap, no solvents. A quality PVC mini ball lasts three to five years of regular home use before the plastic starts to perish. If you spot cracking around the plug or the ball softens overnight, replace it.

The wider context for why this all matters: the NHS adult activity guidelines recommend strength work on at least two days a week, and pilates is one of the listed options. Adding a £10 mini ball is one of the cheapest ways to scale every adductor, glute and core move you already do.

FAQs

What is the pilates ball you put between your knees called?

It is usually just called a pilates soft ball, pilates mini ball or pilates over ball. UK studios also call it a "squeeze ball" or "between the knees ball". They all describe the same kit: an 18cm to 25cm soft inflatable PVC mini ball used for adductor, pelvic-floor and deep-core cueing in mat pilates.

What size pilates between the knees ball should I buy?

For most UK home users an 18cm to 20cm ball is the most versatile. It sits cleanly between the knees for clamshells and inner-thigh work, and you can deflate it down to a lumbar pillow for bridge work. Taller users (5'9" and over) and instructors running progressive thigh-squeeze classes often prefer a 22cm to 25cm size.

Is a pilates mini ball the same as a pilates ring?

No. A pilates between the knees ball is a soft inflatable PVC ball you squeeze, deform, or lean on. A pilates ring (or magic circle) is a rigid 38cm hoop with two pads that gives fixed resistance for squeeze drills. Both train the adductors, but the ball is softer, scales with how much you inflate it, and doubles as a lumbar support. The ring does not.

How firm should my pilates ball be?

Inflate to roughly two-thirds full. The ball should compress under a knee squeeze but bounce back when you release. Rock-hard inflation turns the press into a bone-on-plastic feeling and removes most of the inner-thigh work. Under-inflated balls collapse and lose feedback. Take the time to pump, test, top up, test again.

Can I use a pilates between the knees ball during pregnancy?

Most low-impact uses (between-the-knees squeeze in seated work, lumbar support during articulation) are well tolerated through pregnancy when cleared by your midwife or physio. Avoid supine work after the first trimester. The NHS pregnancy and exercise guidance is the right starting reference, and the Chartered Society of Physiotherapy can point you to a women's health physio in the UK.

How do I clean a pilates soft ball?

Damp cloth, a drop of mild washing-up liquid, wipe down, air dry. No solvents, no alcohol wipes, and no machine washing. PVC degrades faster when exposed to harsh chemicals or heat. Cleaning between sessions is enough for a home ball. Studio balls used by mixed groups should be wiped down between every user.

Why does my pilates ball keep deflating?

Usually the plug is not seated correctly. Pull it out, give it a clean, re-seat firmly so it is flush with the ball's surface. If the ball still deflates within 24 hours, the PVC has likely punctured (often invisible) and the ball needs replacing. A 2015 review in a PubMed-indexed pilates training study found inconsistent prop pressure was one of the most common reasons home users abandoned a routine, so it is worth getting the seal right before you give up on the kit.

Conclusion

A pilates between the knees ball is the cheapest, smallest, most-used piece of kit in mat pilates. Buy an 18cm soft ball for clamshells, inner-thigh squeezes and lumbar support, or a 22cm to 25cm ball if you train more thigh-squeeze and bridge variants. Inflate to two-thirds, store out of the sun, and replace every three to five years.

For UK buyers, the flexa.fit Pilates Ball (18cm) is the everyday pick: anti-burst, latex-free, true-to-size, under £12 with code MEGLIO10 and free UK delivery, no minimum spend. Pair it with a premium yoga mat and you have a full home pilates setup for less than the cost of two studio classes.

This article is for informational purposes only and is not medical advice. Consult a qualified healthcare professional before starting any new exercise programme, especially if you are pregnant, postnatal, or recovering from injury or surgery.