This water gauge is designed for any service including steam. Glass is high pressure Pyrex and is protected by rods which also hold the gauge together. Gauge has valve on bottom to shut off the boiler and a cock on the bottom to blow the gauge down. The gauge should be blown down periodically to make sure water way and steam way are still open. Valve is made of C360 brass. Overall height is 4 1/2", length of valve assembly is 2 1/4". Top fitting is threaded 1/8-27 NTP.