A Japanese product from 1988, sold in the US by a small company in Torrance, California.

In Japan it is called Genki-kun, and it has been on shelves for 38 years.

The product you are looking at is designed and made in Japan by Dr. L Co., Ltd. of Ashikaga, Tochigi Prefecture — a small health-equipment maker that develops everything it sells in-house and manufactures in Japan. Its Japanese name is 足ゆび元気くん — Ashiyubi Genki-kun, roughly "lively toes" — and it sells in a market where foot-care and massage products are an everyday category, not a niche. More than two million pairs have been sold there, in the same two firmnesses and three sizes we sell here.

The story of how it came about is on the maker's own site, in Japanese. The short version: in 1986 the founder, Hiroyuki Funatogawa, set up a small lab and built a motorised device to stretch the Achilles tendon. It was too expensive to make and too risky if it malfunctioned, so he abandoned it — and the prototype gave him the idea for something with no motor at all: a shaped block of foam that holds the toes apart and lets the person do the moving. Two years of development later, in 1988, the trademark was filed. The company name, Dr. L, is borrowed from Superman's father, Jor-El. He says so himself.

The maker's stated principle is "make it to please the person using it, not to sell it." Thirty-eight years on the shelf in Japan is what that looks like in practice.

Two things printed on that box are worth knowing, because we say the same things on this site.

"First-time users, start with Soft." That is the maker's own instruction, on the front of every box sold in Japan. It is also the first thing we tell everyone on the collection pages.

The size chart is the maker's, not ours. The chart on the box is in Japanese sizes; ours converts it to US street-shoe sizes. The slots themselves are identical.

One thing we do differently from the box. The Japanese packaging leads with a slogan about what happens when you wear it. On this site we say something narrower: in the one trial that tested it, wearing a toe orthosis on its own changed nothing, and the movement you do while wearing it is what counts. That is a stricter standard than the box holds itself to, and we hold to it on every page — here is why.

What is different about the US version, and what is not.

Toe-Rx is the name we gave it for the US. Here is exactly what changed when it crossed the Pacific, so that "designed for American feet" means something specific rather than something vague.

If a US customer tells us something about fit, sizing or the instructions, it goes back to the maker — through our Tokyo office, in Japanese, to the people who make it. Improvements happen slowly, at the factory, not on the website. That is the arrangement, and it is the reason the US version stays the same product rather than drifting into something else.