These are just a simple set of caps which act as labels for some PL-259 calibration standards I made. They fit the PL-259 which is for RG-213 cable usually specified as 9mm. The thread is the standard 7/16 UNC 2A used on those plugs. I printed at 0.1mm to ensure the threads are accurately formed but only 20% infill at the most is needed. Print with the letters down on the bed.