Review on Busy Corner Telescoping National Measuring Thickness by Guillo Tilden

This O-Ring Gauge is made of durable plastic, slides freely, the O-ring size markings are printed in white on a blue background making it easy to read. Smaller o-rings can be sized using the exact silhouettes printed on each side of the gauge. All sizes are marked with regular "-dash" numbers for easy locating at your local stock or tubing store. The top of the gauge has slots for the "size" of the o-ring gauge. The instructions for use are clearly printed on one page so that they do not get lost and are easy to understand. The overall length of the sensor is 13.5 inches by 1.25 inches square. As with any retractable gauge, the tension you apply is key to an accurate reading. If it needs to be kept in a toolbox I would recommend you keep the box or have a friend sew a sleeve. This will protect the print from scratches and the grease will make the markings illegible.