The insole aisle is a marketing category. Arch support, gel pods, memory foam, heat-molded promises. Almost none of it is engineered around force return, because comfort is easier to sell than performance.
The claims
Inventor William R. Crow holds U.S. Patent Nos. 5,554,694, 5,695,850, 6,120,880 and 6,589,630 B1, covering the incorporation of resilient performance materials into shoe inserts, insoles, midsoles and soles. They were the first patents ever issued under the performance-enhancing athletic shoe component category.
The material
Springsoles use a proprietary blend including 1,4-polybutadiene, selected for its physical and vibration-response characteristics. Butadiene rubber carries roughly 15% more resilience than any other material in the world; natural rubber contributes flexibility and comfort while holding that resilience together.
The dimension that makes it usable
3/32nds of an inch. It fits beneath your existing insole, snug against the hard surface of the shoe, trimmed to your foot. No size change, no new break-in period, no relearning your footwork — which is why athletes actually keep it in the shoe.
Springbak® — MADE IN THE USA, refined over more than 30 years.
Put it beneath your feet
Springbak® Springsoles — 3/32nds of an inch, trim to fit, $29.95.
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