3/8", 1/2", 3/4" Pex Go No Go Gauge, Helps Ensure A Quality Joint, It Has 6 Openings, 2 For Each Size Of Pipe It Fits, For 3/8", 1/2", & 3/4", 10, 15, 20 mm, Pipe Sizes, Following The Illustrations For Guidance On How To Use This Important Tool.