In its simplest form, a derailleur-alignment tool is often little more than a pry bar with an adjustable feeler. They're often crude, and can be frustrating to use considering the feeler's position is compromised every time it contacts the rim or is moved to clear frame stays. Abbey Bike Tools addressed this issue with the Hanger Alignment Gauge. The feeler can lock into place so it retains position if it bumps against a wheel, and the top half rotates to clear stays -- making full, 360-degree rotation much easier. This means not only quicker, but more accurate alignment. To ensure the hanger position is spot on, Abbey Bike Tools holds tolerances as tight as half a thousandth of an inch (. 012mm) within critical dimensions. The Hanger Alignment Gauge is compatible with most common wheel sizes (26, 27. 5/650B, and 700/29) and is about 28mm long. For easy portability, or to save space in a toolbox, the feeler can be stored inside the top-half of the tool. The Abbey Bike Tools Hanger Alignment Gauge is rebuildable and, for durability, it's powder coated and anodized where applicable.