This is the Zeagle Compact Pony SPG Pressure Gauge Features: Extremely compact Screws into any Scuba HP Port Pressure-at-a-glance Rugged Helps keep your pony bottle neat, organized, and simple Dimensions: 1.25 overall length Only 7/8" extends from the regulator Dial 1" diameter Weight 1.6 oz Sometimes a standard submersible pressure gauge with its large dial, extra weight and long hose is too much for the job. If you want to get a quick idea of how much air is in a cylinder and you do not want to deal with the tangle that longer hoses can present, then a Zeagle Pony Gauge is the answer. Perfect for pony bottles, hang bottles, and even a tank/regulator used for shop air. "