This item is a method called flat HOP.This is a small amount of HOP protrusion, but this can make the BB bullets rotate the HOP long and shallow.And this is a packing intended to reduce the energy loss of BB bullets.Hardness 45. This is softer than Tokyo Marui genuine packing.Supported devices: Tokyo Marui electric gun, PROMETHEUS "delta strike barrel"Can be installed on models with a small amount of HOP protrusion.
