MAD BULL ENHANCE HOP UP BUCKING 2 BUCKINGS IN ONE PACK. How to install: Apply some silicone oil inside and outside the bucking when installing onto the barrel and into hop up chamber. Tech Note: Hop-Up Buckings are wear items and should be changed as often as feasible. And should be replaced when upgrading or anytime the inner barrel is removed from the hop up unit. Small pin holes and tears can occur when removing and reinstating used buckings.