Hi quality vinyl - as the car is never going to have a roof, it's inevatibly going to get wet at some point. I didn't what to go to the expense of leather only for it to get trashed later on. I'm also not feeling so light now. Merlin have rung me to advise that I should really go for the SuperSport version of the belts with the normal style seatbelt catch, as the IVA man wouldn't like the aircraft style buckle. Apparently the MOT testers don't like them either... Which is a shame, as I do. Boo. Anyway - I've gone with their suggestion, but the upside is they're considerably cheaper!