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