Polarstar Barrel Shim O-rings, 10pk

10x pack of 8x1.5mm O-rings for barrel shimming Replacements for if original O-rings were lost, or more O-rings are needed for shimming the barrel. The O-rings are to be installed on the barrel and butted up against the front of the hop-up. The O-rings provide a more rigid option for biasing the hop-up assembly towards the gearbox, ensuring the hop-up will not move away from the nozzle tip during use. This is a common method for stabilizing the hop-up, and works well with other HPA systems, as well as AEG systems.