L.J. Star Metaglas Type 61 sight glass products comply with the recently revised ASME standard for electric boilers, Section I PEB-13, Water Gages, allowing the use of a bull’s-eye-type fused sight glass window on boilers with a diameter of 16 in. or less. The sight glass products screw into a vessel without external mounts or gaskets. Constructed of borosilicate glass, they are resistant to erosive and corrosive chemicals, and can be used in a range of applications including circular assemblies for welding onto vessels, weld neck and nozzle flanges, and visual flow indicators.