A cylinder is fitted with a yoke with a sealing washer like Bodok seal. LCPs bodok seal is made of noncombustible material and has a metal periphery which makes it long lasting. It should be less than 2.4mm thick prior to compression and only one seal is allowed between the valve and yoke. If more than one washer is used the pins may not extrude adequately to fit in the holes. Thus pin index system may be bypassed and a wrong cylinder may be attached.