Box Two Chain Tensioner Two Hole 10mm Blue lets you dial in just the right chain tension for smooth, reliable riding. With two mounting holes, you’ve got ample adjustability to suit a range of frames, keeping your rear wheel aligned and secured. Built from rugged 6061-T6 aluminium and finished with anodised, laser-etched graphics, this tensioner protects frame dropouts and helps prevent chain slip for a steady ride.