It really is fairly easy to measure suspension sag or race sag with a metric tape measure, but those rigid-aluminum sag tools with the pin that goes inside the rear axle make it much easier. We have them, but unless you have a boxvan or an enclosed trailer, they generally stay in the garage. That means they aren't at the track, where you need them. Until now.
By necessity, most sag scales are too long to fit in a toolbox. Noleen, however, cleverly put a hinge in the middle of its device, so the scale locks opensomething like a folding pocket knife. The red-anodized aluminum tool is very handsome and as handy as any of the rigid one-piece models. The Noleen sag scale performs on par with the others yet fits easily in an average toolbox. We have it with us and use it almost every time we ride; we can easily recommend a product we use that often. The price is $29.95.