Mitutoyo Inch Rectangular Gauge Block Set Series 516-927, Thin Block Set - 10 pieces grade AS-1A gauge block set with all blocks made of special tool steel, heat treated and aged to give good wear resistance and small secular change. Excellent inter set wringing properties and will wring to optical flats or gauge blocks made of any other material. Mitutoyo Inch Rectangular Gauge Block Set Series 516 927, Thin Block Set 10 pieces grade AS 1 Select Gauge Block Sets Thin Gauge block sets in steel Grade AS 1 Material Steel Number of Pieces 10