Resin or metal

A phase usually ment as a choice directed towards one's own sexual partner to pick a cock-cage that is either made of metal or a metal like material, or resin. Usually most associated with petplay, BDSM, or any of it's sub categories.

Person 1: "Which cage do you want on? Resin or Metal?"
Person 2:"I haven't gone with the resin cage in a bit so I guess resin it is"