Airtech Studios ICS CXP-MARS PWD9 BEU Battery Extension Unit Ares  Built-in standard height adjustable

 Built-in standard height adjustable back up iron sight

This thing is awesome

Action Army VSR-10 CNC Tactical Receiver

We recommend the 9

and optics

Airtech Studios ICS CXP-MARS PWD9 BEU Battery Extension Unit Ares  Built-in standard height adjustableThe Airtech Studios ICS CXP MARS PWD9 BEU Battery Extension Unit is designed to fit on PDW 9mm style AEG guns. May also fit on other ICS PDW rear buffer tubes as well. Very easy to install so you can add longer and bigger batteries in your rear stock buffer area. With it installed, you can use longer 11. 1v batteries in it, with extra room to spare. This is a must have for those that want flexibility with battery space. Can fit up to a Titan 3000 nun