1,CE certificate 2,reliable after-sale service 3,OEM is ok Diameter: 40mm, 50mm, 60mm, 70mm,100mm...Connection: bottom, back connectionThread: 1/8", 1/4",3/8",1/2" NPT,BSP,BSPTInternals: BrassCase & bezel: Black metal,plasticLens: Plastic windowAccuracy: 2.5%