Nasstoys of New York The Macho Collection Silicone Duo Cock & Ball Ring Black. The Duo Ring is a pair of silicone rings for cock and ball play. Increases sensation in the scrotum & penis shaft. Constricts blood for thicker girth. Pleasurable pressure and tightness. Phthalates free cock and ball ring, gates of hell set. Materials: Silicone rings, PVC strap. New image added 2/19/2014.