Set of thread gauges both inch and metric. Each part contains a thread pitch gauge, and a corresponding hole the diameter of the noted thread. Hole diameter is 0.25mm oversize to allow correct size bolt to pass thru. All have a 5mm hole for mounting. NOTE The smaller thread pitches may not print correctly on a FDM printer, laser cutting is recomended for these parts. For a different take on a screw checker more compatiable with FDM printers please see Thread Gauge Cone: http://www.thingiverse.com/thing:153820 Credit where credit is due: Mr. Smout (http://www.thingiverse.com/Smoutech/designs) put out the challenge to come up with a thread gauge and bolt checker so I am happy to oblige.