The latest product video from RA Tech features their Blue Rubber which is their replacement hop-up rubber for KWA Gas Blowback airsoft guns. They demo it using the inner barrel set with the KWA HK45 Gas Blowback Pistol which can increase the fps from around 350fps to 360fps. With THE KWA LM4 GBB Rifle, from around 460-480fps and with the new hop-up rubber, the rifle's hitting at 501-530fps.