Insole and foot terminology

Clear, neutral definitions of the terms used across our guides and product pages — from the materials we print in to the parts of the foot an insole supports.

TPU (Thermoplastic Polyurethane)

A flexible, hard-wearing plastic used in 3D printed insoles. TPU keeps its shape under repeated loading while staying springy and light.

Shore A hardness

A scale that measures how soft or firm a flexible material is. Lower Shore A numbers feel softer; higher numbers feel firmer.

Additive manufacturing

Building an object layer by layer from a digital model, rather than cutting or milling it from a solid blank. Also called 3D printing.

Arch support

The section of an insole that supports the longitudinal arch of the foot, helping to distribute load more evenly across the sole.

Heel cup

A cupped section at the rear of an insole that cradles the heel, keeping it centred and cushioning impact.

Footbed

The insole or liner inside a shoe — the part your foot rests on. Most shoes have a removable footbed that can be replaced with a custom insole.

Pes planus (flat feet)

A low or collapsed arch where more of the sole contacts the ground than average.

Pes cavus (high arches)

A pronounced arch where the foot contacts the ground over a smaller area, concentrating load on the heel and ball of the foot.

Plantar fascia

The band of connective tissue running along the sole of the foot from the heel to the base of the toes.

Pronation and supination

The natural inward (pronation) and outward (supination) rolling motion of the foot during walking and running.

Orthotic (orthosis)

A device placed inside a shoe to support or correct foot mechanics. Custom orthotics are shaped to an individual foot; insoles4.me products are non-medical comfort and support products, not medical orthotics.

EN ISO 20345

The European standard for safety footwear, specifying protection requirements such as steel or composite toe caps. Replacing the removable footbed in a certified boot does not normally affect the boot's protective rating.

Metatarsals

The five long bones in the midfoot that connect the ankle bones to the toes. The heads of the metatarsals bear much of the load when standing and walking.

Heel-to-toe drop

The height difference between the heel and forefoot of an insole or shoe, measured in millimetres. A higher drop places the heel above the toes; zero-drop keeps the foot level.