Oil Fillers Oil fillers with air breather caps serve two purposes which are important on hydraulic installations:They permit easy oil filling of the installation and they avoidthe introduction of large dirty particles or objects into the tank.They filter and clean the exchange of air between tank and outside ambiance when there are flow variations. Data Sheet Send an Inquiry Product Codes of Oil Filler Series TR: TypeDimensions (mm.) TypeMicron FilteringRecommended FlowøABøCDøEøFFixing Holes TR-1402504535826627413 TR-2407007545839548736 TR-34070075458315048736