RCBS Casemaster Gauging Tool-A quick, convenient way to determine several important case and cartridge dimensions. The CaseMaster gauging tool measures case neck concentricity, case neck thickness, case length bullet run-out. All are important to accuracy and safety. Detects case head separation before symptoms are apparent on the outside of case. Much quicker than a dial caliper and makes a tedious job simple and less tiring. Dial indicator accurately displays various measurements to .001" for the discriminating hand loader who demands a higher level of ammunition performance.