19 mm
thingiverse
A customized version of the design can be found at http://www.thingiverse.com/thing:44815. It was created using the Customizer app with specific settings: groove set to 1, type as 0, weight at 11, margin of 0.1, edges enabled, cursor positioned at 100, diameter of 19 and 50 faces ($fn).
Download Model from thingiverse
With this file you will be able to print 19 mm with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on 19 mm.