L.E. Wilson has been making precision reloading tools for over 80 years. This gauge allows reloaders to measure case length from the base of the cartridge to the shoulder, as well as the maximum case length. This process shows the reloader if ammunition is being produced within industry specifications. Notes: This is a two-piece, adjustable cylinder-type gauge for checking fired and resized cartridge cases for cone-to-head and overall lengthUsed to compare cartridges against the minimum and maximum SAAMI cartridge dimensions Instructions from the Manufacturer: Drop a fired case into the gauge. Take a measurement on headspace. This can be done with either a depth micrometer or caliper (Depending if the case is sitting high or low in the gauge). If the case sticks out past maximum headspace the firearm probably has a larger than average chamber. The gauge can still be used because it is being used to determine how much resizing is required.Now once the initial measurement is taken, sl...