The Heavy Hex Gauge - is a simple bolt size gauge that, from one flat is an identifier of the ASME Heavy Hex Nut sizes and corresponding ASME stud sizes. This both a stud, bolt and nut sizer. Rather than measure across the flats, the Heavy Hex Gauge nut measuring tool measures as a nut checker from one flat or one side of the hex nut, bolt head or stud. Easier than a bolt board or cable type bolt nut gauge because it works on installed nuts. It's one of those popular field machinist tools commonly used by Millwrights, Pipefitters, Field Technicians, and bolters who work in Power Generation, Chemical Plants, and in the Oil & Gas industries. It's a great gift for men who work in these fields as a handy tool and could use a nut and bolt sizer. It is both a bolt sizer and a nut sizer made for jumbo nuts and bolts and large head bolts as a sizing gauge that identifies only standard sizes. The bolt checker bolt sizing gauge or bolt size tool measures the outermost part of the thread so it's easy to identify a standard bolt size. Make fast work at sorting your bolt bin. Most technicians will wear this sizer on their lanyard with their badges. This version fits easily a shirt pocket or keep it on your pocket tool keychain as a keychain tool. The Heavy Hex Gauge nut size gauge only has tick marks for the standard sizes so our gauges have no other sizes to confuse you. It is a simple nut bolt measuring tool that, from one flat, the nut gauge measures and identifies the ASME Heavy Hex Nut sizes and corresponding bolt measurement gauge and all are based on ASME stud sizes. Kind of like having your own standard bolt size chart. That fastener standard is based on ASME 18.2.2 the plastic is UV coated to keep it from fading in the sun. Packaging includes 10 Heavy Hex Gauges in protective vinyl sleeves.