Nearly all electropneumatic markers work with compressed air (no CO2 as it freezes with high rates of fire) and they all require a battery in order to work.
Inner operations of the marker are electronically controlled enabling the use of several different fire modes, such as full automatic or ramping and changing the maximum and minimum rate of fire.
Due to electronic operation the weight of all moving parts can be reduced allowing for a reduction of input pressure as well. Lower operating pressure combined with low recipicating mass offers the user less felt recoil and smoother operation, also making possible the use of brittle shelled paintballs.
Most electropneumatic markers also feature break beam eye system that won't allow the marker to fire before a paintball is properly seated in the breech, this eliminates barrel breaks and empty shots.