Hi there,
I have tried 3 different sizes o-rings for my brown Zowie Celeritas and my brown Filco Majestouch2. Here my experience ....
http://img4.imageshack.us/img4/1595/oring.jpg2 bought at a local store - the last one at WASD
http://www.wasdkeyboards.com/index.php/products/keyboard-accessories-2/cherry-mx-rubber-switch-dampeners.htmlSee pic for different o-rings. The last are the ones from WASD, they do not follow the European measurement of 5mm diameter and thickness is about 2mm. It is less diameter which makes it harder to apply them on a cap. They seem to be silicon as well in terms of softness which is good.
I would describe the difference between those 3 - in terms of sound als non-existent (between them!) and tactile wise it is minimal. However if you buy the 1,5mm o-rings, you can apply 2 rings per cap and shorten the travel way significantly. Without rings it is 2mm to the point of contact - then 2 mm to bottom out. Afterward I would say only 1mm is left to bottom out. You can not apply 2 o-rings 2mm thickness as this will make the cap stick up higher out of the keyboard and will not minimize the travel and in case of the Celeritas it wont hold as firmly on in keyboard as there is almost nothing of the key cap "stomp" left to stick into the switch everything is covered with rings. The key caps of my Filco has a longer stomp. 2 o-rings on a Filco is possible.
In every case 1 or 2 rings the sound will change as the cap itself will no longer bang on the plate below. (unless you really hammer on a key with you fist)
For games where I press one button more than once rapidly (e.g. starcraft2) I prefer to have a shorter travel way which is which is why 2 o-rings are a good solution for me. (arrow buttons for example)
