Kenyan long-distance runner Eliud Kipchoge won yesterday’s London Marathon with Nike’s Flyprint brand shoe, which is believed to be the first-ever 3-D printed performance footwear.

As Yahoo News first reported, the shoes were made with a printer re-engineered specifically to create shoes for performance, which means a softer, more customizable fit than other 3-D running shoes. Information gathered from three-dimensional scans of Kipchoge’s foot strike over time is fed into the computer, along with Kipchoge’s personal feedback, to produce an upper that is unique to him.

The top part of the shoe is printed layer by layer in a special blend of thermoplastic polyurethane (TPU) filaments, known for elasticity, transparency and resistance to abrasion and liquids. Water resistance is important for runners who wish to prevent their shoes from getting saturated and heavy. The TPU material, when laid flat, looks and feels like a more supple window screen, with patterns that vary from the forefoot to the heel and on the sides.

The top, which takes just 30 minutes to print, is attached to a sole made from two layers of Nike’s ZoomX foam with a carbon fiber-articulated plate sandwiched in between. Kipchoge said he felt the difference in how his muscles responded to his most difficult training sessions.

“The shoes are really light,” he says. “And they absorb all the impact from the ground. When you run with this kind of shoe with all the efficiency inside it, to recover, it’s really fast. When you step on the ground, there is no impact at all, no soreness in the muscles.”