Miyota 6S21 quartz movement with chronograph and date functions Stainless steel case Case diameter: 49 mm Case height: 17,5 mm An enhanced hardened 3.5 mm thick mineral K1 crystal Water resistant up to 30 ATM / 300 m An automatic helium release valve. It is integrated in the watch case spring-loaded one-way valve activated when the difference between the inner and the outside pressure reaches a critical level. This function is useful for commercial divers operating at great depths using diving bells with breathing gas mix inside Swiss-made tritium tubes mounted vertically of on the dial ring. Such position of tubes provides additionally advanced illumination of the time indication Leather and silicone straps interchangeable by just one screw driver An original construction heavy duty stainless steel buckle The whole watch set packed into an original VE waterproof and shock-resistant plastic box, which can be used during extreme activities to keep valuable possessions safe