XS Scuba's Regulator Necklace is derived from Technical Divers that had a need to keep their Back-Up Regulator close when needed. The Regulator Necklace is made from soft yet durable silicone rubber and is perfectly designed to fit around a diver's neck, with or without a hood keeping your auxiliary air source close. Necklace will not stretch out of shape with the No-Memory Silicone Rubber design. XS Scuba's Silicone Regulator Necklace is available in two sizes: Regular with a 7.5" (19.1 cm) Diameter and Large (for Pumpkin Heads") with a 10" (25.4 cm) Diameter.