The SPI 52-piece fractional inch gage ball set includes 26 pairs of grade 24 accuracy gage balls. Precision accuracy: grade 24 (AFBMA certified) with 0.0001" Tolerance. 26 pairs of gage balls from 1/8" to 1" diameter: 1/8, 9/64, 5/32, 3/16, 7/32, 1/4, 9/32, 5/16, 11/32, 3/8, 13/32, 7/16, 15/32, 1/2, 17/32, 9/16, 19/32, 5/8, 21/32, 11/16, 23/32, 3/4, 13/16, 7/8, 15/16, and 1 inch. Chrome steel is hardened to 63RC. Ground and lapped. Includes sturdy case.