Didn’t Help Much with GMK/ePBT
The foam is cut precisely and fits well but, at the 3.5mm size, it doesn’t help much with sound. I’d honestly just buy something denser like sorbothane and cut it yourself. You’ll likely get better results from that.
Absolutely Phenomenal (NOT FOR PLATE MOUNT STABS)
Do you have screw in PCB stabs? Buy this for your larger/thin spacebar. I bought the MT3 (6mm) and it fit snug as a bug. This also fits Tai Hao cubic profile spacebars which is what it will be used for. Tai Hao cubic spacebars are much thinner, and so the sound produced is a bit high pitched for my liking. These foam inserts changed the game for it, producing a fuller deeper sound. To be honest, I'm not even removing the adhesive strip as it doesn't move after placed. NOTE: They're so precisely cut that with plate mount stabs there is an extra housing around where the stab mount goes into the housing, and so it will not let the spacebar depress. It hits the foam where with a PCB mount stab there is nothing for the foam to come in contact with.
Very Nice but It has a Major flaw
I bought these a few days ago, while testing out some durock plate mounted stabs. When I got to testing out the spacebar I decided to install this foam on the spacebar. Just to figure out it doesn't work with traditional plate mounted stabs. I would recommend going with these anytime if you are going to use screw in stabs but if you are going to use plate mount you shouldn't buy this. In summary these are amazing 10/10 would recommend unless your using plate mounted stabs and then in that case you might has to do some modifactions to the foam.
Be wary of Drop Alt fit
I bought the 3.5mm foam for my regular cherry profile spacebar and it worked fine in my KBD67 Lite R2. Not a huge difference but it does mute the louder sound of my space bar out a bit which is what I wanted. However, I also bought the 9.5mm foam for my SA keycaps and found I could not push the spacebar down on my Drop Alt at all. The 3.5mm foam spacebar is difficult to press down on the Drop Alt as well. Both foam sizes work fine on my KBD67 Lite R2. I would say if you have a Drop Alt to be wary of buying any size of these foams.
Perfectly fits GMK space bar, not to thin, not to thick so the space bar doesn't feel mushy.