1.5mm thickness silicone O-ring, sized to fit on the inside of Cherry MX keycaps to reduce the sound from keys hitting the bottom of their stroke.
40A Shore rating.
Pack of 110 allows fitment to 104/105 key keyboards with a few to spare.
Key Puller available separately:
Available in a pack of 110 rings at a slightly lower price here:http://www.kustompcs.co.uk/acatalog/info_30041.html