The Backstop Core 2.1 Gallon Potable Water Expansion Tank 3/4 NPT is a reliable and durable boiler expansion tank designed by ELBI. This white tank has a capacity of 2.1 gallons and features a 3/4 NPT connection for easy installation. The Backstop Core model is specifically designed for HVAC and refrigeration systems, making it an essential part of maintaining and improving the efficiency of your system.