Doc Johnson Kink Leather Master Ring Black Red Cage. Your sub knows who is in charge, but a thrilling display of your prowess never hurts. Slip your cock and balls into the Leather Master Ring from the Kink by Doc Johnson collection and reap the erection-boosting benefits of the leather cage straps and ball splitter and extreme metal o-ring. The Master Ring will not quit until you do. Specifications: color Black, Red. UPC Code 782421060152. Ring inner diameter 3.5 inches, metal ring 1.95 inches. Materials Leather cage, Silicone ring. Kink by Doc Johnson is an exciting collaboration with Kink.com to create a collection of high quality authentic fetish items suitable for long-term practitioners and new initiates alike.