This is an E-grip upgrade for the BT Slice or BT-4 Combat and can be installed within seconds. It has 3 firing modes: Semi-Auto, 3 Round Burst and Full-Auto (up to 13 bps). Double Trigger for faster firing, Sleek push button Controls, Visual LED Indicator. Operates off a single 9 volt battery. Great upgrade if you’re looking for a little more out of your BT Slice.