With the MK25 EVO/A700 you are guaranteed a reliable, low-effort delivery of air, no matter how hard you're breathing, how deep you're diving, or what your temperature gauge reads. The MK25 EVO first stage lets you enjoy an ultra-fast breathing response, instant delivery of air on demand, great sensitivity and extra-high airflow, regardless of how cold the water is. The A700 second stage, with its metal casing, screw-down cover, metal valve housing (barrel) and over-molded accents, exhibits a real muscularity in design. Put them together and you get unparalleled breathing performance whether you're cruising the balmy waters of the tropics or venturing beneath a polar ice cap.