Dead Air Silencers Odessa Booster Shims 2 Black. The purpose of adjusting tension of your booster spring is to allow for better cycling of your slide on a tilting barrel handgun. You can use zero one or two shims to experiment with and adopt one of three different levels of spring tension. Specifications for Dead Air Silencers Odessa Booster Shims 2: Manufacturer: Dead Air Silencers Color: Black Features of Dead Air Armament Dead Air Odessa Booster Shims 2/ct: Odessa Shims Odessa Piston Booster Spring Adjust Tension Better Cycling Tilting Barrel Handgun Package Contents: Dead Air Armament Dead Air Odessa Booster Shims 2/ct Dead Air Silencers DA015: Odessa Booster Shims 2 Black