Scubapro MK21 300 DIN First Stage

The Scubapro MK21 DIN 300 is a compact sized piston-controlled first stage.

Close to 20% smaller than Scubapro’s MK25, MK21 is a mid-range air balanced, first stage. Air balanced pistons deliver significantly more air to the second stage than any other first stage, while their performance is totally unaffected by the changing tank pressure. A balanced piston allows the use of lighter and more sensitive components, resulting in ultra-fast breathing response, instant delivery of air on demand, and extra high air flow, especially in low tank pressure ranges. The tired diver benefits from a smoother breathing regulator during the ascent or deco stop. Balanced piston first stages are the first choice of demanding sport divers and professionals.

A balanced piston performs equally in warm and cold-water environments.


The Scubapro MK21 First Stage offers the best compromise for the right price and the right performance with ease of maintenance. Cold water diving with Scubapro-Diving conditions can be drastically different, including extreme cold water and outside temperatures, posing the possibility of a regulator “freezing”. Therefore, resistance to freezing is imperative for the diver. All Scubapro Regulator Systems are CE approved for 3336 psi (230 bars) cold water diving. Some models go even beyond this super stringent qualification and have successfully been tested in extreme cold diving conditions at less than 3.9°F (3.9°C). As a specific anti-freezing measure, Scubapro engineers have designed a patented finned cap for the MK21 First Stages for optimal cold-water diving. This finned cap is a Thermal Insulating System (TIS). The ribs of the TIS act as a radiator to increase the surface area of heat transfer from the water to warm up the internal parts that have been drastically cooled down by the gas pressure drop.

The Scubapro MK21 First Stage is manufactured from marine grade chrome plated brass, has a balanced composite/stainless steel flow-thru piston and with the standard head it has 4-HF (High Flow) 3/8″ threaded low-pressure (LP) ports with hose routing at +/- 20° angles and 2 7/16″ threaded high-pressure (HP) ports, one on each side of the body. The MK21 First Stage weighs 19.6 oz. (555 g) with externally adjustable intermediate pressure which allows authorized Scubapro service technicians to quickly fine-tune and adjusts the first stage after maintenance without the need to disassemble it.