This gun is used by the US Navy Special Forces as well as countless Tactical Teams. One of the best weapons on earth for building entry and room clearing. The SD2 BT Version features: Full B&T Logos, all metal body, metal front set, metal silencer, metal gears, advanced hop-up and a high torque motor. If you are looking for a high-end BT5, this is it. Weight and feel are excellent, not to mention the performance. The larger stock will allow for great upgrade potential. With exceptional accuracy, a high rate of fire and stand-alone power, the SD2 is on the top of our list for BT5's. Classic Army has done a tremendous job with this airsoft version.