Hi quality CNC machined solid brass inner barrel made in japan and processed by ultra polished finish enlarged hop packing hole and final special cone to reduce output turbolence the Bright Coating process reduce the airloss and industrial defects.... combined with the 6.05mm +-0,01 tollerance, make the bb flight straight and far..... compatible with SRE & standard electric guns suitable for MARUI, G&G, G&P, VFC precision inner diameter of 6.05mm length: 260mm