luthj
Engineer In Residence
That may be the variance between factories or production runs. However, if you get all your sheets from the same production run, they will likely be withing 1/16" of each other, with minor variance. I have used foam board in varying thicknesses for plug/mold setup and some composite parts over the years. I have seen maybe 1 or 2 sheets that were defective, and had "major" variances in thickness.