Ball bearing washer/cone

i have printer this universal spool holder.
http://www.thingiverse.com/thing:572371

found that when it try to tighten the nut on both side with a ball bearing and normal washer there will be pressure on both side causing a lot of tension when unwinding.

so i made this the bearing cones these are made of 8mm..

if you wish to resize it go ahead :D

the red thingy in the middle of the nut and the ball bearing.