Replacement Sealing O-rings. 
One replacement set of (4) Vinton O-rings for 2 Stroke pipe collar. 
Fits pipe collar pn#  EC-BT2
Fitment From Parts Finder:
BETA (20-25) 200RR  With FMF pipe and FMF Turbine or Power Core 2 Silencer
Also Fits Models Below:
BETA (19-25)  250 /300 RR   With  FMF pipe and FMF Power Core 2.1  Silencer & Turbine Core 2.1 ( NOT 2.0)
BETA (15-25) 300 X-TRAINER  With Stock or FMF pipe with FMF Turbine or Power Core 2 Silencer
         
        
          Replacement Sealing O-rings. 
One replacement set of (4) Vinton O-rings for 2 Stroke pipe collar. 
Fits pipe collar pn#  EC-BT2
Fitment From Parts Finder:
BETA (20-25) 200RR  With FMF pipe and FMF Turbine or Power Core 2 Silencer
Also Fits Models Below:
BETA (19-25)  250 /300 RR   With  FMF pipe and FMF Power Core 2.1  Silencer & Turbine Core 2.1 ( NOT 2.0)
BETA (15-25) 300 X-TRAINER  With Stock or FMF pipe with FMF Turbine or Power Core 2 Silencer