1-1/2 NPT Thread Stainless Steel Oil Sight Glass,Oil Viewports,Level Window For Air Compressor Gearbox Vacuum Pump Differential
https://www.vogueparade.com/shopping/EN/200282142/1/1005003694969671/1-12-npt-thread-stainless-steel-oil-sight-glassoil-viewportslevel-window-for-air-compressor-gearbox-vacuum-pump-differential//