This miniature dual barrel shotgun allows to shoot form his barrels modified bottle rockets (with the tail removed). the gas port on the barrel allows the exhaust gases from the rocket to escape reducing flash and pressure allowing for a safer operation. (guide for modifying rockets on pictures). Bolts required for assembly (thread x length): -4mm x 20mm (minimum) (A) -4mm x 15 mm (minimum) (B) -3mm x 15 mm (minimum) (C) Warning, this model is not a toy, bad use can result in injury always shoot straight into the air and have fun! I'm not responsible of any damage or injury realized with this model. Enjoy the build! :D