Amped Airsoft got the fully licensed PTS Centurion Arms CM4-10 that uses the KWA ERG system. It comes with the EPG, EPS, and EPBUIS from PTS as well. This is rear wired and can take in Lipoly batteries as power source... "Amped Airsoft's Wes gives quick review about the PTS - Centurion Arms CM4-10."