ScubaPro MK11/S270 Regulator Yoke For divers seeking reliable performance in an uncomplicated air delivery system, the MK11 / S270 is easy to use, compact, and durable. The balanced diaphragm MK11 delivers effortless airflow unaffected by depth, tank pressure, or breathing rate. The compact S270 provides smooth breathing performance in a bulletproof anti-scratch design that’s able to handle years of hard use.