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. cm) diameter and large (for pumpkin heads") with a 10" (25.4cm) diameter.