The Element 55% Hop Up Bucking comes with the bucking, hop up spacer, barrel spacer and barrel bushing. The bucking and spacer are pretty self explanatory, the white plastic barrel spacer is made to keep the inner barrel steady in the hop up unit in front of the bucking. As for the barrel spacer, it's made to go near the front of your inner barrel to keep the front steady inside the outer barrel. It may not work on all applications, and is not completely necessary, but definitely a nice thing to have just in case.
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