1.5mm thickness silicone O-rings, 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:
110 rings should be enough to cover for a UK keyboard with up to 5 macro keys. If you need additional rings (eg for keyboards with a quantity of macro keys, Corsair K90 / K95) you can find extra additional rings here:http://www.kustompcs.co.uk/acatalog/info_30255.html