Custom build done a couple years back. Gearbox is running great with tons of upgrades shooting around 30 rps with 11.1 batteries. Hopup is a little finicky and could use a rebuild and adjustment. Tappet plate also seems to have left the chat. Great tuner gun. Not sure on specifics of upgrades. but looking for 300$ for gun alone with 30 per 6000 mah battery and 20$ per 3000 mag. 25$ for the mags 425$ total plus shipping. Shooting video available upon request