One thing regarding Pre-Cuts is that the 4 thicker thicknesses (in all sizes),  .050″, .075″, .100″, & .125″ are NOMINAL thicknesses, so the marked value may NOT necessarily be the actual thickness; therefore you MUST measure them to be certain that you know the actual thickness.
There are many different brands on the market. Some have closer tolerances to the nominal thickness than others. Some are very “liberal” in the actual vs marked thickness. Some brands mark them with the actual value to the nearest .001″ (example .102″ or .076″ vs. .100″ or .075″. I have seen some that are marked to the nominal thickness to be off by as much as .005″ from the marked nominal value.
This is important to know because if you “assume” that the marked thickness is the actual thickness, you may be adding or removing the wrong amount when making shim changes, or creating a Soft Foot condition. It is always a good idea to measure each of the four thickest shims.
Another thing to look at with Pre-Cuts is the edges of each shim. One Brand CONSISTENTLY has a ridge on either side; I have measured this ridge to be as much as .005″ thicker on the edge than the rest of the shim. This shim will produce a Soft Foot that you can’t get rid of on all four feet. It’s like inserting leaf springs under the machine’s feet.
Conclusion: Pre-Cut shims’ quality can vary greatly. Poor quality shims can make the alignment process very difficult. Be careful which one(s) you select!
Thanks to Roy Loop with The Rueck Company for this valuable post.

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, by Ana Maria Delgado, CRL