The L7 Bolt for the PMR is a bolt system that is designed to be the lightest possible. The L7 is specifically designed to decrease marker "kick" and increase accuracy. All of our bolts run faster and smoother than any other bolt system available. Those that have tested this bolt have said that the kick reduction from this bolt is amazing. At any given pressure and dwell this bolt yields about an extra 10-15 FPS over the stock bolt.The PMR L7 Bolt now comes with spacers to change the operating pressure of the marker. With no spacers the bolt system will shoot 300 FPS around 140-150 PSI. With one spacer as shown here, the bolt will shoot 300 FPS at 150-160 PSI. With two spacer the marker will shoot 300 FPS at 190-200 PSI. The spacers make the operation of the marker more adjustable to your preference. The Proto Rail is a pretty awesome marker. However the stock bolt system has a large amount of kick when set up to shoot 300 FPS. The stock set-up feels a bit "chunky". This kick, or "chunkiness", knocks you out of aim, and ultimately makes you shoot more to hit your target. This causes you to win less, and get shot more. The L7 is designed to change that. Our patent pending "reduced kick/high speed internal system" allows you to stay on target better, shoot faster, and hit the target more quickly than ever before.You will be amazed at how much better your marker feels and shoots.