The BOLT B4 MK18 Mod I Block II gets reviewed by Geonox Airsoft. Just like the others in the B4 Series of Bolt Airsoft, this features the Blowback and Recoil Shock System (BRSS) of Bolt for their AEGs. This is a full metal AEG with ABS PistolnGrip and glass fibre-reinforced stock. As this is a rear-wired AEG, the battery compartment is located in the Crane stock.