... glasses, sight gauge, sight gage, oil level indicator, liquid sight glass, sight window, view ports, male thread sight glasses Body material ... : aluminum, brass, PC, PPMA and steel Glass: Real glass 2 mm to 5 mm thickness. O Ring: Viton O ... Usage: Pump Gearboxes, Speed Reducer, Compressor and Power Transmission. Different company have different requirements, OEM Service is welcome.