Some time ago, I have read with great interest CPTBasAss' review of O-rings and landing pads (a link to his review has been given in a post above).
At that time I already had O-rings from The Keyboard Company. I think they are the same ones as CPTBadAss' reds, the ones without the dots. They are 1mm in width and they are soft. I had already tried them in two Filcos TLK (one with browns and one with blues). I had even tried to stack two O-rings (stack three and your keys don't work anymore
).
After reading CPTBadAss' review, I ordered several sheets of black landing pads from EliteKeyboards.
If you are looking to reduce the keyboard's noise, the best are black dampeners, followed closely by one O-ring, and the worse (but some could like it) is two stacked O-rings.
Black dampener (landing pad): I confirm they reduce the bottoming-out noise a lot, and your fingers will feel the impact much less. The travel of the key is not reduced much, it's barely noticeable. I recommend them!
One O-ring per key: reduces slightly the travel of the key, but by less than 1mm (the ring has a width of 1mm, and you compress it a little bit when you bottom out, so you still have a little bit more than 3mm of travel). The feel of the keystroke is more faithful to the unmodified key: you still feel the impact when you bottom out, but it's less hard. The noise is slightly louder than with the black dampeners.
Two O-rings per key: it's an interesting experiment. You bottom out immediately after the actuation point. So you always bottom out, however there are two O-rings to dampen the impact, so it's rather quiet. But now the travel of the key is very short (just a little bit longer than 2mm). If you like laptop keyboards, you may like it. I have kept the mod for several days on my Filco with browns, and it's actually usable and I'm sure some people would like it.
So long story short,
I recommend the black landing pads from EliteKeyboards, or any equivalent model (is there any other shop that sells them?).
NOTE1: landing pads are tricky for backlighted keyboards. I have modded a KBT Pure Pro with them, but the landing pads sometimes rotate a little bit and the when the corner of a landing pad ends up in front of the LED, the corresponding key is visibly darker than the other ones. In order to avoid this, I recommend O-rings for keyboards with backlighting. I solved the problem differently, by glueing the dampeners to the keycaps (with very very small amounts of glue). I even took advantage of this to have some keys darker than some others, for aesthetical reasons. But it's a lot of work, so if your keyboard has backlighting, just use O-rings, which is exactly what I have just done with my second KBT Pure Pro.
NOTE2: reducing the noise on bottoming out is fine, but a lot of noise comes from the impact of the key when it travels back into its "up" position. I have managed to reduce this noise by using grease, but I'm not sure it's the correct way to do it. I'm not even sure the board will not die from this!
NOTE3: I realize I should definitely try two black landing pads per key!
I would like to thank CPTBadAss for his review of dampeners, it was very interesting and useful.
