Each shim is ground on 6 sides with two magnets on the bottom face, there are 7 different heights and 4 pieces of each height in a set. These shims have countless uses around the shop and also in combination with our squares.The magnet sizes are carefully chosen so that the taller shims have enough magnetic force to hold them up sideways on a project while carrying some of the smaller shims. The thinner shims have smaller magnets which reduce the amount of force required to remove them. The shims are ground on all 6 sides to an accuracy of +/-0.0009 which is less than 1/1024 of an inch! Think of a 1/32” reading on a machinist rule, now divide it by 32 again to get 1/1024 of an inch.
Shims are hardened to HRC 50.Just remember, to properly measure these you need to use a micrometer mounted on a stand and with the shim wiped clean. A pair of calipers in the hand with a dirty shim will not get an accurate measurement.