TheFloatStopO₂SMFLTBBreathingCircuitGas(BCG)isavailableintheflowtubekit.Alongwiththefloatstopthekitcontains,filter,O-rings,springandtube.Aflowmeterconsistsofflowtubemoduleandflowheadmodule.Thesmallandlargeflowtubescontainsmallandlargefloatstopsrespectively.ThereareseparateflowtubekitsforO₂,N₂0,CO₂andair,sincetheyarecalibratedtoaspecifictubeandinterchangingfloatscancauseincorrectreadings.Thefloatstopissuspendedintotheflowtubebyaspringonthetop.Whenoxygenisforcedinbetweenthetubeandthefloat,adifferentialpressureisgenerated.Thefloatstopsatanareawheretheupwardforcecausedbydifferentialpressureandthedownwardforcecausedbytheweightofthefloathavebeenequalized.Theresultingdisplayistheoxygenflowwhichiscalibratedwiththetube.