타입 = Drill Hole Gauge Number of Pieces = 4 Largest Diameter = 12.7mm Smallest Diameter = 3.2mm PVC wallet. Starrett Small Hole Gauge Set. A small hole gauge set which can be used to determine bore sizes. Precision tapers expand the ball end to the bore size, and can be measured with an external micrometer.,The expansion range of the tapers is limited by internal stops.