The Trumark RR-1 is designed for use with Trumark Slingshots. They work well as replacement bands for my tree branch slingshot too. The left and right bands are cut from one length of tubing so the wall thickness is "matched" (balanced) for accurate shooting. Trumark's pure, surgical-latex powerbands are packaged straight in sealed, air tight, plastic blisters that prevents band deterioration. Installation instructions are included on the package. 225 Yard + Range!