For those who don't know these nuts have castellations in them to allow the insertion of a split pin so that the nut cannot unscrew itself by vibrations.
These little guys are crimps that you generally find on the end of air hoses and the like. I added a couple of texture layers to it too.
(By the way, the gauge that you were all guessing the other day is an
engine compression test gauge, which tests the cylinders in an engine to
see if they have got the correct compression)