Walk into any pharmacy and you'll find a shelf of things labeled "heel inserts." Some are foam. Some are gel. Some are cork. Some are adjustable. Some are clearly designed for comfort, others for height, others for therapeutic use. The labels don't make the differences obvious, and choosing the wrong type for your specific situation can mean months of discomfort — or worse, a problem that gets harder to fix.
This guide cuts through that. It explains what the different types of heel lifts are made of, how they perform in real use, and which type makes sense for which situation — whether you're managing leg length discrepancy, recovering from Achilles tendonitis, working with a prosthetic, or just trying to improve your golf game.
This distinction matters more than most people realize, and getting it wrong is the most common mistake people make.
A heel lift is a firm wedge that raises your heel by a specific, consistent height. It doesn't compress under your weight. Its job is to change the mechanical position of your foot — correcting a leg length discrepancy, reducing tension on the Achilles tendon, leveling a tilted pelvis, or improving gait mechanics. Think of it as a precision tool.
A heel cushion or pad is a soft insert designed to absorb impact and protect pressure-sensitive areas. It's appropriate for heel spurs, plantar warts, arthritis flare-ups, or just sore heels from a long day on concrete. It's not appropriate for therapeutic elevation. When you compress a cushion by standing on it, whatever height it appeared to have disappears.
This guide is about heel lifts — the firm kind. If you're looking for impact cushioning, that's a different product category entirely.
Is your need temporary or long-term? If you're using a heel lift to treat Achilles tendonitis during a recovery period and then tapering off, you need something adjustable — you'll be changing the height regularly. If you're compensating for a permanent leg length discrepancy and expect to wear a lift indefinitely, durability and shoe comfort become more important.
How much elevation do you need? The practical ceiling for in-shoe heel elevation is about 12mm — roughly half an inch. Above that, the heel sits too high within the shoe and the ankle loses stability. Some people are uncomfortable with even 10mm depending on shoe style.
Smaller feet typically tolerate less height than larger ones, and lace-up shoes accommodate more than slip-ons. More than 12mm of correction has to involve external modification to the shoe — adding height to the sole itself, not just inside it.
What shoes are you putting it in? A closed-heel shoe is the easiest and most stable environment for a heel lift. Sandals and open-heel shoes are harder — most lifts become visible and unstable in them. Athletic shoes generally need a firmer lift than dress shoes because the foot is exerting more lateral force during movement.
Cork has been used in shoe orthotics for a long time, and for good reason. It's lightweight, relatively inexpensive, and doesn't crush significantly underfoot. Cork lifts are typically covered with leather or vinyl to protect the surface and extend their life.
Best for: Ladies' dress shoes, where weight and thickness matter. Daily use in shoes where you want modest, comfortable elevation without something heavy underfoot.
How to use them: Cork lifts can go either above or below the shoe's insole. Placed under the insole, your foot still rests on the original cushioning — the cork simply adds height without adding bounce. This is particularly important when using a lift in only one shoe for leg length discrepancy: with a firm lift under both insoles (or a lift under one and nothing added to the other), both shoes feel similar to walk in.
What to watch for: Cork is the least durable of the firm options. It will wear down over time and need replacing more often than plastic or multi-layer vinyl lifts. It's also not ideal for active sports — better options exist for athletic use.
Molded plastic lifts are more durable than cork and hold their height better over extended daily use. They're a solid choice for work boots and men's everyday shoes where longevity matters and weight isn't a concern.
Best for: Long-term leg length discrepancy compensation in durable footwear. Post-surgical or prosthetic applications where a specific, consistent height needs to be maintained over months.
What to watch for: Plastic is rigid. The inside of a shoe isn't always flat — some have curved heel pockets, some narrow, some wide — and a rigid plastic lift doesn't conform to those variations the way more flexible materials do. This can create pressure points or an awkward fit in shoes with unusual heel geometry.
Quality also varies significantly. Better plastic lifts are injection-molded, which produces consistent thickness and accurate height.
Cheaper cast plastic lifts can vary in actual thickness from what's labeled. If you're buying plastic lifts for precise therapeutic use, pay attention to how they're manufactured.
Standard heights available are typically 3mm, 5mm, 7mm, 9mm, and 12mm — fixed choices, no adjustability between those increments.
This is where most of the consumer market lives, and it's also where most of the problems come from. Foam and gel heel lifts are widely available, inexpensive, and aggressively marketed — and for therapeutic use, they're largely the wrong choice. Here's why.
The compression problem: Every foam or gel material compresses under body weight. That means the height you measured when you bought it is not the height you're actually getting after an hour of walking. And it means your heel is moving up and down inside the shoe with every step — bouncing on the foam, then releasing. That vertical motion is friction. That friction causes blisters, calluses, and direct rubbing against the Achilles tendon. For someone trying to treat Achilles tendonitis with a heel lift, using a foam lift can actively make the tendonitis worse.
The height illusion: Because foam compresses, the effective height is always less than the stated thickness — sometimes considerably less. A foam lift labeled 9mm might give you 5mm of actual elevation under body weight, and that number changes as the foam gradually crushes permanently over weeks of use.
The moisture problem: Open-cell foam absorbs sweat. That creates odor and bacteria growth. Some manufacturers explicitly label foam heel lifts as disposable and recommend replacing them every three weeks. That's not a feature — it's an acknowledgment that the material degrades quickly.
The one situation where soft material makes sense: Cushioning a specific pressure point. If you have a heel spur or plantar wart and you need to offload pressure from a small area, a thin gel pad positioned precisely over that spot is appropriate. The goal there is pressure redistribution, not elevation — and gel does that without the height compression problem that makes foam unsuitable for lift use.
For any therapeutic heel elevation — adjustable heel lifts for leg length discrepancy, Achilles tendon therapy, hip alignment correction, back pain management — firm material is the right choice. Not foam. Not gel.
Adjustable heel lifts are the most versatile option and, for most therapeutic applications, the most clinically useful. Instead of being manufactured at a fixed height, they're constructed from multiple thin layers — peeling one off reduces the height, adding one back increases it. Each layer typically represents 1mm of elevation.
Why adjustability matters — practically:
When you start wearing a heel lift for leg length discrepancy or short leg syndrome, your body needs time to adapt. Muscles, tendons, and joints that have been compensating for an imbalance for years don't immediately feel better when you correct it — sometimes they feel strange or sore at first as the compensation pattern unwinds. Starting at a lower elevation and increasing gradually over weeks lets the body adapt progressively instead of being shocked into a new position.
When you're tapering off heel lifts after Achilles tendon treatment, you need to reduce elevation gradually — the tendon re-lengthens slowly, and removing the lift too abruptly risks re-injury. An adjustable lift lets you reduce by 1mm at a time on whatever schedule your provider recommends.
When you need a slightly different height in your dress shoes than your work boots, adjustability lets you optimize each pair rather than accepting a compromise.
The transparency advantage: The Clearly Adjustable heel lift is made from a clear vinyl material that molds to the shape of the shoe's heel pocket when placed under the insole. This means it conforms to the shoe rather than sitting rigidly in it — both shoes end up feeling similar regardless of their individual internal geometry. The transparency also makes it nearly invisible in sandals and open-heel shoes, which is where most other lifts fail visually.
The design advantage: The lift's long constant slope — running from the heel well forward toward the arch — prevents bridging. Bridging is what happens when a lift is too short: the heel is elevated but the arch is left unsupported, suspended between the lift and the ball of the foot. That causes arch strain and discomfort that most people incorrectly attribute to the lift itself rather than to its insufficient length. Longer is always better in heel lift design.
For leg length discrepancy and short leg syndrome: Use a firm lift — cork, plastic, or adjustable vinyl — placed under the insole. Both shoes should feel the same, which means a firm lift that doesn't add softness or bounce in one shoe but not the other. If you're new to heel lift use or still dialing in the right height, an adjustable heel lift for leg length discrepancy is the most practical starting point.
For Achilles tendonitis: Firm material only. The heel must not move up and down in the shoe during walking or running. An adjustable lift is particularly useful here because you can start at a therapeutic height and reduce gradually as healing progresses — a fixed-height lift locks you into a step-down that's too abrupt. Go firm. Go adjustable.
For prosthetic and rehabilitation use: Precision and adjustability matter more here than in most other applications. The ability to change height in 1mm increments — and to fine-tune the height as gait patterns shift during recovery — is clinically significant. Firm, adjustable lifts used under the prosthetic footbed or inside rehabilitation footwear are the preferred option.
For athletic shoes, running, golf, skiing, and skating: Firm only, no exceptions. Soft lifts in athletic footwear create lateral instability that can cause ankle sprains, particularly during any movement involving directional changes. Even modest foam compression creates instability that compounds at speed. A firm, thin adjustable lift under the athletic shoe's insole is the appropriate choice for both leg length discrepancy correction and general heel-pocket adjustment in sports footwear.
One detail worth getting right: heel lift height should be measured at the point where your heel bone — the calcaneus — actually rests on the lift, not at the very back edge. The back of a well-designed lift curves to match the heel pocket of the shoe, which means the back edge sits slightly lower than where the heel actually contacts it. Measuring at the back edge overstates the functional height. Measure where the straight sides of the lift begin.
If you're not sure which specific product is right for your situation, the best next step is a conversation with a podiatrist, chiropractor, or physical therapist who can measure your leg length discrepancy precisely and recommend an appropriate starting height. Armed with that information, choosing the right lift becomes straightforward.
The Clearly Adjustable heel lift is available from several authorized vendors — find them below.
On This Site
Where to Buy Clearly Adjustable Heel Lifts — Authorized vendors carrying the Clearly Adjustable heel lift, available online or by phone.
Sizing Information — How to measure your heel pocket and choose the right size. The right size is determined by heel pocket width, not shoe size.
Usage and Customization Instructions — How to place, adjust, trim, and maintain the Clearly Adjustable heel lift for specific conditions including leg length discrepancy, Achilles tendonitis, and sports use.
Leg Length Discrepancy and Short Leg Syndrome — What causes leg length differences, how the body compensates, and how heel lifts address the underlying imbalance.
Achilles Tendonitis and Heel Lifts — How heel lift inserts reduce tendon strain, why firm material is essential, and how to taper elevation as healing progresses.
Heel Lifts in Active Sports — Why firm material is non-negotiable in athletic footwear, and how to use heel lifts safely in running shoes, ski boots, and other sports footwear.
Varus/Valgus Wedging — How to configure the Clearly Adjustable lift for side-to-side angular correction without changing heel elevation.
Why Not Use Heel Lifts? — An honest look at what can go wrong with heel lift use, and how to avoid the most common problems.
Opinions and Experiences with Heel Lifts — A balanced review of the clinical debate around heel lift use, including the inventor's own decades of experience managing leg length discrepancy.
Rehabilitation and Prosthetic Use — Specific guidance for post-surgical recovery, stroke rehabilitation, and prosthetic fitting applications.
Golf Swing Improvement — The peer-reviewed research behind heel lift use in golf and the documented improvements in distance and accuracy.
Disclosure: The author of this guide, Richard W. Zehr, is the manufacturer of the Clearly Adjustable Heel Lift and has personally managed a moderate leg length discrepancy using in-shoe heel lifts for several decades. The comparisons and recommendations above reflect genuine experience with the full range of heel lift products, not marketing opinion. This information is presented for educational purposes and is not intended as medical advice. Always consult a qualified healthcare professional for therapeutic applications. ©2002–2025 Clearly Adjustable.