Kink Endure Premium Silicone C-Ring Set Black. The Endure C-Ring Set includes three sturdy cock rings in extra thick silicone flexible enough for safe use but firm and unforgiving enough to grip your balls and shaft hard. The three different sizes have the range to fit every wearer in multiple ways, guaranteeing powerful marathon erections, explosive orgasms, and pleasure so intense it almost hurts, in a good way. Features: heavy duty extra thick Silicone. Strong and pliable ring stretches to fit. Enhances and prolongs erections. Phthalate free, body safe. Specifications: color Black. UPC Code 782421059668. Ring inner diameter 1 inch, 1.5 inches, 1.75 inches. Material Silicone. 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.