Gas Boiler Spare Parts Universal New Copper Casing Single Tube Heat Exchanger For Squirrel Gas Boilers Features : 1 Material : copper tube , aluminium fin , galvanized plate and stainless steel plate 2 foil : Hydrophilic or naked three kind :Louver Fin , Flat fin , corrugated fin four of fins can be adjusted between 1 5 of holes and pitch of rows:19*16mm,21*21,21*19mm 6 less than three air strain (nitrogen)leak examine 7 can supply custom-made carrier besides Our store also has different kinds of gas boiler heat exchangers ,if you need ,please seek the advice of custom carrier