AnO-Ring,also knownasapacking,oricjointisatypeofagasketorasealintheformofaringwithacircularcrosssectionusedtopreventleakageoffluids.O-ringaremadeupofavarietyofmaterialincludingViton,Neoprene,Silicone,EPR,PTFE,PUorNitrileRubber(alsoknownasBUNA-N).This12.37mmO-RingismadeupofaSiliconeCompoundthatisflexibleandresistant temperatures,fungalgrowth,UVandozoneexposure,andweathering.Siliconeoffersgoodtemperatureresistancebutitisnotsuitableforusewithpetroleumbasedoils,oracids.SiliconeO-ringsareanexcellentleakagebarrierandarewidelyusedinmedicalequipmentsandBreathingGasCircuits(BCG ). Theyareseatedinagrooveandcompressedbetweentwoormorepartstherebycreatingasealattheinterface.