R-hop kit from HS Armory. The R-hop variants are the ultimate hopup system, not only greatly increasing accuracy, but also range at the same velocities. These patches distribute the pressure on the BB better than any other system available including flat-hops and any after market bucking. Contains three patches to allow for experimenting and multiple installs.
If you live in a cold weather area, the IR-Hop is recommended, as it is very resistant to temperature change.