Tension Chucks for Striping Round Parts - Scale Modelling

I needed to add a stripe to many (30+) round parts. Ideally i wanted to spin the parts on my Dremel and then use a paint brush to apply the stripe, but i could not find anything to allow me to simply hold the parts, so i made these.

The chuck fits into the dremel. It has 4 finders and a stop to hold the part in the same place every time. There are 6 parts in 2 different finger diameters (2 and 4mm). The 6 parts are at distances from the finger tips of 5-17.5mm in 2.5mm increments, allowin