Standard Steel Liquid Level Gages can be used to view liquid levels in hydraulic reservoirs, tanks, large steel mill pumps, gearboxes, bearing housings, crankcases, transformers and machinery oil reservoirs. Their use can be extended to any industrial liquid level viewing application. This sturdy gage is made of plated steel. The glass sight is protected by steel on three sides. A red line on a white background enhances liquid level visibility. Leak-proof construction is achieved with Viton seals. The unit tolerates up to 125 PSI and 300° F. Fluid enters through the cross hole in the hollow lower bolt. The gage is vented into the tank through the cross hole in the top bolt. The length between the center of the two bolts is referred to as the center line. The distance between the center of the tank holes must be within 1/32” of the center line measurement. This gage is mounted to the tank with (2) 1/2”-20 plated steel bolts. The back mount design requires that the inside of the tank be accessible in order to secure the bolts with plated steel hex nuts. Torque to 90 in-lbs.For fractional inch centerline distances, level markings or other seal options, please consult factory.