Description: MadBull Shark Hopup Bucking x 2 + Fishbone Spacer x2 How to install: (1) Please apply some oil outside the bucking when installing. (2) Also, remember to replace the spacer to the X type one. NOTE: X spacer is not good for all AEG. (3) If you have problems to shoot out B.B., please apply some oil "inside" the bucking. About this product (FROM MAD BULL) Shark Hopup Bucking is original designed for 470 to prevent double feeding. By 3 special "fins" inside the bucking, Shark Hopup Bucking can hold one and only one B.B. tightly in the chamber. In the mean time, to our surprise, we found that this bucking could enhance the velocity on some AEG. But not all AEG could have the same results and the result could be different from one AEG to another. Unfortunately, we don't the exactly reason because each AEG has its own condition. However, we do believe that the friction (from 3 fins) applied onto B.B. will enhance the velocity.