Crater and hole measurements are always in microns, and are given to one, sometimes two, decimal places!  We don't claim to have any outlandish hardware in our laboratory; we have decided to provide the measurements as calculated by our software, and you can truncate them as you see fit.

In the case of smaller MLI perforation holes, where the minimum hole diameter lies quite relatively far below the surface, the edges can be quite indistinct: in these cases uncertainties can be around 10% or sometimes more (rough estimate).  For larger craters the errors are far smaller (I would give them only a few percent).

There are quite a number of elliptical holes in MLI as well.  In these cases we have measured the area of the inner edge of the crater (as for the circular holes) and taken the diameter to be that of a circle of the same area.  We think this method is acceptable within the range of the observed hole ellipticities.

The images are not all taken at the same magnification ­ for each case we chose the highest magnification which could conveniently fit the hole within the screen.  We do not provide magnification information on this site, as they are of not much use without calibration measurements.  We already measured up all the features and assume you will trust our values.  However, if you should like to take your own measurements from the images we provide, please mail me for image calibration data.