Center finder

I created a simple tool to help you find the center of a cylinder. Included here are one SolidWorks file with various configurations for the small (25mm), medium (50mm), large (75mm) and XL (100mm) versions; this dimension pertains to the overall width or length of the device. Also included are the STL files.
Note that the diagonal was created with a slight (0.75mm) offset for the width of the marker (see pics). After some trial-and-error I determined that this was a pretty good offset distance