More firing modes , better grips. Hard to adjust the sear & fit the battery
Over all a good improvement for the bt, transforms it into a totally different gun IMO. Could have had more options and a slightly better construction. low battery indicator, easier to change firing modes without opening it up.. Although i suppose this could have been designed this way to keep it simple and durable.
My conclusion is buy it, but be prepared to get a better hopper and read my review first, cheers.