Replacement o ring pack for inside the bottle on the following air rifles.

Parts 1, 5 and 7 on the diagram

FX Crown & Crown MK2
FX Boss
FX Gladiator & MK2
FX Verminator & MK2
FX Impact MK1, MK2, M3 & M4
FX Maverick
FX Royale
FX Verminator & MK2
FX Wildcat MK3 BT

Video below of replacement