This tool makes measuring pick up shoe springs easy and consistent. The scales are all set to read a .010" high rail reading. Scales do have some variance from scale to scale, the tool is used a reference of knowing that your car runs best on this track at 3.0 grams(your neighbors scale may be 3.3g)
If using high tensions you may need to lightly hold down the front end to get an accurate reading. This tool is very useful quick and easy to use and comes with a nice pouch to protect it.