USPSA Magazine Gauge by Springer Precision 

USPSA 140mm (141.25mm) and 170mm (171.25mm) mag go-no-go guage. We precision machine these gauges so that you can verify your magazines are legal for your divsion BEFORE the big match. These are machined to the USPSA specifications and which are not the same as IPSC specifications, so beware if you shoot USPSA and international IPSC matches that you use the right guage. (NOT LICENSED BY USPSA FOR PERSONAL USE ONLY NOT MATCH ADMINISTRATION)