AP0540C/DS4 ATX40 REGULATOR DS4 A-CLAMP AP0540C-1/DS4 ATX40 REGULATOR DS4 DIN Tried and tested ATX design, entry level regulator – ideal for beginners, school and rental kit. Second stage - pneumatically balanced, adjustable venturi. Features heat exchanger to protect against freezing – so ideal for diving all over the world, even in the coldest waters. Environmentally dry sealed, balanced 1st stage. No swivel turret. 4 medium pressure ports and 1 high pressure port. Finished in highly polished chrome. Oxygen compatibility kits available. 1st stage ports: 4 x 3/8” UNF & 1 x 7/16” UNF