Remember when you had maximum precision? The WEN 81-Piece Rectangular Steel Gage Block Set provides machine accuracy and reliability all in the palm of your hand. Each steel block has been machined exactly to its claimed dimensions, making these the perfect tools for the calibration of measuring equipment and more. Each individual set includes a unique certificate of inspection showing you the idiosyncrasies and deviations (accounted for in millionths of a meter) that may exist within your gauge blocks. Includes the following various sizes: 9 blocks ranging from .1001 to .1009 inches (.0001-inch step), 49 blocks ranging from .101 to .149 inches (.001-inch step), 19 blocks ranging from .05 to .95 inches (.05-inch step), and 4 blocks ranging from 1 to 4 inches (1-inch step).