A few years ago, I spent a few months working on a long-form piece about the nascent world of 3D-printed footwear; a piece that ultimately died on the grapevine but brought me deep into this new world. My reporting led to two conclusions: there are some extremely exciting new companies and designers making cool work with this tech; but most using it are not.

By printing a shoe in layers of soft, flexible plastic, shoe companies can produce shapes and cushioning that are impossible with classic injection mold technology. The Japanese brand Aliveform has taken full advantage of this, releasing a lineup of incredibly unusual shoes, of which I now own six pairs. Readers are welcome to read more about the brand in my recent piece on them for our digital pages.

Aliveform is the standout though, as despite the added cost and time of 3D-printing, most shoes on the market are just far more expensive TPU mules. You can buy a pair of Beluga slides or Murcielaco Spider mules for $159 and $499 respectively from German 3D-printing brand Zellerfeld, but an Adidas Yeezy Slide or Foam Runner costs a fraction of the price, even on resale, for better results, and is available immediately.

However, some brands have been using 3D-printing for performance rather than aesthetics, and interesting developments are happening here. For a few years, Adidas pushed its “4D” printed mesh-midsole technology. It’s less comfortable and performant than its best foams, but it has some interesting new flexing qualities that they keep developing. The most interesting use of this though comes from Holland’s Ecco, whose BIOM Infinite M has two different uses of 3D printing that no one else has tried before.

From a design perspective, they look like an alien’s idea of a classic workout sneakers. They blend unusual lace holes, random patterning on the recycled knit and perforated leather upper, and an organic-looking outsole that seems to grow onto the upper. As a result, though most of Ecco’s mainline sneakers look rather derivative, the Infinite M is a truly distinct, compelling design, albeit undermined by poor colorways.

I chose the white pair, which by far looks the best but is rather plain, doesn’t show off the unique design of the Infinite M, and has proven rather stainable. The other options were an even plainer all-black colorway and a heinous orange and brown, which nobody should wear. They needed matcha gradients, or dip-dyes, or a bold all-blue; colorways that match the special vibe of these shoes. Ecco’s in-house tannery sells some of the most beautiful, unique leathers on the market, so they could have even used some of these too.

Regardless, it’s what’s under your foot, not around it, that gets interesting. The entire midsole is a 3D-printed unit like a thick insole that can be slipped in and out for three different purposes. The least interesting of these is the “Ultralight Core”—a relatively conventional all-foam unit that provides moderate support and is handy for sprinting and other running where you just want the lightest experience underfoot. The “Performance Core” and “Stability Core” are truly special as they’re 3D-printed silicon mesh midsoles of differing density and can be printed according to your exact weight and height. The stability core is noticeably stiffer and denser, whereas the “Performance Core” is printed with a wider mesh making it more bouncy underfoot.

The result is interesting and handy for someone who does varying exercises. You can put the varying cores in your gym bag and switch out when needed. When skateboarding, I use the “Ultralight Core;” when running or doing general gym workouts, I use the “Performance Core;” but when I move to heavy weights or play an on-court sport, I switch to the “Stability Core.” Are they as good for running as a performance running shoe with foam and a carbon shank? No, but they’re meant to be an all-around performance shoe, and for their first outing in this sector, Ecco has done an impressive job.

In the future, Ecco intends to make replacement cores available to purchase, therefore lengthening the lifespan of your shoes, but the cores have held up well since I started using them in October, so I doubt this would be a regular occurrence. Unfortunately, the upper and outsole haven’t been so durable, with my usual sneaker-cleaning solutions proving insufficient to remove marks and stains.

This is an experimental limited product though, and I expect the team at Ecco to innovate and iterate further on what is already a great core product. For a second version, I would suggest Ecco make a harder, more durable upper and outsole, and counter this by using softer cores and insoles; and also to play with more materials in their cores, to really make them performant. One can imagine a “Running Core” that combines their 3D-printed silicon with a carbon shank, or an “All-Day Core” that uses pockets of foam wrapped in their silicon mesh.

I also think they should offer a version with a heavily perforated all-leather upper, made with more experimental stylish leathers from their tannery. Yes, this would make the shoes heavier and less breathable, but it would also make them wear better, which is core to a shoe built around sustainability and long-term use.