Depends on which carbon arrow you are talking about.There is your standard S-nock that will fit most carbons with a .246 ID.Like GT,Beman ICS,Blackhawk Vapor and some others along with aluminum with uni-bushing 20XX and larger.Then you have your Axis/MFX that take a X-nock with a .204 ID.Then your G-nock that usally require a bushing,they have a .166 ID.Then you have your H-nocks that are inbetween a X-nock and a S-nock.With your S-nocks they are a few different brands to pick from.For me my preferred S-nock or some call a Super nock I like Easton 3D Super nocks.The other nocks mentioned there are not many choices other the Easton.The G-nock though comes in two different throat sizes.A large groove with a .098 throat and a small groove with a .088 throat.