OTR SERIESOPEN-TYPE REEL, ULTRA-GLASS BLADE, STANDARDA Keson best seller! Since 1968 this style of Keson fiberglass tape has beenproviding customers with accurate measurements. They are used in the harshestconditions in which people measure, and they stand to the only test that matters:field performance. We cover each blade with two coats of PVC protected by doubleshield, one to bind the fiberglass strands and a second over the printed units, so thenumbers don’t wear away