EFI FG904 6-5/8" Clear Flat Glass Single Window Boiler Water Gauge Insert Clear Flat Glass Boiler Water Gauge Inserts For Steam* Pressure up to 900 PSI @ 534_ F With Mica Shield Heat-treated flat glass with mica protection makes this EFI Gauge Insert an efficient, boiler water level indicator. Finest quality borosilicate glass of special composition to resist temperature shock is carefully tested for surface trueness and assembled with best quality sheet mica in heavy forged steel housing. The mica resists corrosive effects of steam and water. Clamping of the 900 PSI design features individual "fingers" which assemble easily and promote uniform bolt pressure to assure gasket tightness. The assembly is easily dismantled for cleaning and other maintenance. Window slot 1/2" wide provides a highly visible gauge reading which can be accentuated by using an EFI Illumination Assembly. Made in single and multiple-window style to handle a wide range of visibility requirements. Minimum centers shown apply to use with EFI SG854 or EFI SG860 **WARNING: For use with POWER BOILER SATURATED STEAM APPLICATIONS ONLY. MODEL EFISG STEEL GAUGE VALVES ARE NOT TO BE USED WITH SUPERHEATED STEAM.