This listing includes your standard calibration cube and cylinder for using digital calipers in understanding your printers size variances. 

Also included is a design rule model to help determine printer limitations and desired tolerances. The sketch of the center hole diameters is included in the listing. The peg printed off to the side is set at a 15mm diameter. Use the two to compare which hole gives ideal tolerance for your design (loose fits, axels, tight fit, etc.).

On one of the sides of the design rule checker determines the width of the line your printer can handle (and yes, a .4mm nozzle can make a .2mm line). It goes from 2mm lines and decreases by .1mm all the way down to .1mm line width.

The other side determines how close you can bring two structures together without bridging the two. Gaps range from 2mm and decreases by .1mm increments down to .1mm gap width.

Having digital calipers for this would be helpful. This model was designed using a video series by Paul McWhorter but I made some heavy changes to make print time shorter and reduce waste. Video on walking through use of these models is linked below.

https://www.youtube.com/watch?v=jItmqubttTI