The 2 inch Brass SPG is for the beginner or the most advanced technical divers. The Hollis 2 inch Brass SPG Comes with a Luminescent face plate with an operating range of 0 to 5000 PSI or even an option for 0 to 360 BAR. The Hollis 2 inch Brass SPG has a chrome plated brass housing and uses a bourdon tube for calibration and accuracy. Equipped with scratch resistant glass. The Hollis 2 inch Brass SPG is oxygen cleaned for use of pure Oxygen or specialty blends for stage and deco bottles or just plain old Nitrox mixes