A Hobie Wave,(Super Wave). I believe this was done by Rick White, here is the link.
I used it as the album avatar, & placed it first to honour the dedication this man has done for Hobie, & Beachcats in general.
There are other parts available, however my only personal experience is with the Harken product line.
You are looking for Part #165 (drum), & #164 swivel. The newer ones will have the part # stamped on the top of the drum, or barrel of the swivel. Here are the links. Sorry, I can't make these links live.