Combination gauge - rivet, drill, & screw 3 in 1 set. Rivet Gauge - measure pop rivets & blind threaded inserts, 5 inch ruler. Internally threaded screw gauge - size bolts & screws, inch & metric, #0- 3/4 coarse & fine thread inch, 6mm - 16mm metric, also a drill & tap gauge on reverse side. Drill bit gauge - inch & metric diameters, 7 - 1/2 inch ruler. Resists water, alcohol, oil & grease. Reliable and accurate.