Tube Cap (second variation, new, reproduction) for Crosman 600, 677, etc. Screws in to pierce the CO2 cylinder. Includes urethane O-ring part number CRS150-054U. For those who are not familiar with the 600, the first variation cap had a hole in the middle and the cylinder went in neck first (second and third variations went in neck last) and the piercing mechanism was in the gun not the cap. The Second variation had the piercing pin in the cap and when tightened, it pierced the CO2 cylinder, then you backed off 1/4 turn. The Third variation cap had a push button piercing mechanism built into the cap.
