This Aeris Pony Bottle Fill Pressure Checker Gauge is available at a great price. This item features: Threads directly into any standard first stage high pressure port Nitrox compatible to 100% O2 Reads up to 5,000 PSI Large numbers and colored read indicators for easy viewing One-way safety valve Perfect for back-up or stage bottles Measures 7/8 wide by 1" long Also great for double checking for hoseless transmission computers This is a great gauge to monitor the air pressure in our tank. "