R-Hop is the single most important part in airsoft that extends your effective range to over 60m/200ft. Max range of 90m/300ft can be achieved (with M130 spring, 1.7J). Package includes: R-Hopped ZCI 6.02mm Tightbore Barrel. An extra R-Hop, Modify Baton Flat-Hop Bucking. This R-Hop is Extremely hard to fabricate due to the 2X 95 degree cuttings. 12 Lengths to choose from: 229mm, 247, 275 300, 340, 363, 380, 407, 430, 455, 509, & 550mm. R-Hop works best with 300-509mm. 550mm requires large air volume to push and is suitable for HPA. 229-275mm cannot take full advantage of the R-Hop. Traditional R-Hops are 1.5mm thick and airsoft barrels are 1.25mm thick. Thus, sanding is required. Our R-Hops are Exactly 1.25mm thick. Therefore, NO SANDING is required.