A UHMWPE Challenger Approaches

So who’s going to bite the bullet…for science of course.




Dude! Huge thanks for sharing. Science!


Ha, yes!

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What would be a perfect housing for these?


Bobba’s, of course !


Definitely look at the disclaimer on the seller’s page. It seems that the stems may not fit into tighter tolerance housings in which category Outemu might fall into.

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I’ve heard that the other ones work really well with Cream housings - that’s why I picked up some of these. I’ll be trying them in all kinds of stuff, and I imagine other folks here will as well.

I also decided to pick up some Gateron Yellows while I was at it as a sort of comparative baseline that’s easy to reference.

It’s funny, I’ve been looking for a place that has good ol’ Gateron Yellows at a non-inflated price (looking at you, mechanicalkeyboards dot com), and/or that isn’t coming from China on a bulk shipping container with a really wide range of possible ship dates, none of which are soon.

I’d find sites that look like a really great deal until the shipping comes into the picture (hi, kbdfans I still love you but I’ve balked at the shipping stage a few times now). Across the board, the real cost of the yellows averaged in the mid to low 30 cent range. That’s not expensive generally, but it might be a little high for those switches.

Shipped from 415 to my neck of the concrete woods, they’re between 27 and 28 cents each. That’s a bit more like it. :+1: I could probably pay a little less with patience, but not having any when it comes to getting parts is definitely a factor. :grin:


MechKeyAlpha has them and offers Hong Kong Post Air Mail shipping for $10 or free if you buy $80 or more.

So 18 cents a piece if you grab a bunch of stuff and hit the free shipping mark, or 27/28 cents if you eat the shipping.



Update 1: So far, none of these are holding onto keycaps at all unless I turn the cap sideways. :grimacing:


I am having the same issue with mine, unfortunately… Also there is some more side to side wobble than the original stems I replaced. I could look past that if the caps would stay on.


That was my biggest complaint with the v1 Invyr’s though it doesn’t seem to be quite as bad as these. On a separate note, the Alpacas I got (from the first round I think) have really undersized stems – I can only use eBPT caps on them as brand new unmounted GMK or JTK sets fall right off.


Update 2: More information:

Caps these don’t seem to hold onto:

  • Ducky OEM PBT
  • NK PBT
  • Those clear caps that come on testers
  • SP SA was iffy but might be workable

Caps these stems do hold onto:

  • ePBT Cherry profile
  • GMK Cherry profile
  • (by extension probably OG Cherry if not too worn)
  • Rando thin painted ABS OEM caps that came with a budget board

This mostly jives with what Sam from 415keys told me; that the target spec for these is original Cherry.

He requested a video, so if you don’t mind my weird voice you can see how these stems fit with a few different caps here.

Also worth noting:

Housings that don’t seem to work well:

  • Tangerine (definite no-go)
  • Boba (might work with lube but I have doubts)

Housings that worked fine:

  • Cream; a little wobbly
  • Gateron (opaque black housing from Gat Yellow)

At least pre-lubing, those housings the stems did work in seemed less smooth with these stems than without, but that’s definitely first-impression territory. These might be better with lube, a break-in period, or different housings - this is just what I’ve found so far with limited testing.

When I swapped one into a Gat yellow and pushed it together with a stock one stem-to-stem, the UHMWPE stem depressed more slowly, and with some slight herky-jerky movement. The feeling is pretty similar to brand-new Cream, with those bits of “stickiness” on slow presses.

So - my recommendation for these stems is to only buy them if you have keys you know to be close to that spec; GMK, ePBT, original Cherry caps that haven’t been mounted and un-mounted a bunch of times, or caps that otherwise fit snugly - AND if you manage your own expectations for these to be an interesting experiment rather than a magic buttery-smooth bullet.


I wonder if UHMWPE shrinks more than some of these other plastics. I feel like every iteration has had some tolerance issue.

From what I understand, yes. UHMWPE shrinks more than many other plastics and it’s apparently challenging to predict by how much.