Accurately and quickly measures chain slack. Two scales measure both chain slack and chain to swingarm clearance in millimeters. Setting chain slack properly dramatically improves chain life. Light weight compact design fits easily in your tool box or road kit. Works on most street and dirt bike applications up to 75 mm chain slack. Made from engineered nylon with aluminum measuring scale. Anodized laser-etched precision measuring scale. Patented design. Note: Refer to your owner’s manual for proper chain slack and procedure.