Shroud back cover, has an o-ring housed inside Ref: FX19588
FX 19588 is the rear part of the FX liner compatible with:
FX Impact compact, standard and super sniper (MKI, MKII, X, M3)
FX Maverick compact, standard, sniper
FX Wildcat MKI MKII MK3 compact and sniper
The following FX serial numbers are compatible FX Impact Shrouds :
FX 19131 Shroud tube 28x157mm valid for FX Impact compact liner, 500mm barrel.
FX 19692 Shroud tube 28x270mm valid for FX Impact standard liner, barrel 600mm.
FX 19142 Shroud tube 28x447 valid for FX Impact super-sniper, barrel 800mm.
The following FX serial numbers are the compatible FX Maverick & Wildcat Shrouds :
FX 19573 Shroud tube 28x230mm valid for FX Maverick & Wildcat compact, 500mm barrel.
FX 19099 Shroud tube 28x345mm valid for FX Wildcat standard liner, 600mm barrel.
FX 19142 Shroud tube 28x447mm valid for FX Maverick & Wildcat sniper liner, 700mm barrel.
Check Shroud tube thread, metric thread M26.5:1.5 thick thread.
If your moderator Shroud thread is fine see the following part: FX 19737