Darts Practice Rings (15-50mm dia)

Designed and created these darts practice rings similar to those on sale from darts manufacturers. The inner diameter of the rings are between 15 and 50mm in 5mm increments.
I designed these to be used along with a sewing needle or a thumb tack of diameter ~1mm to improve the accuracy of my throw. Simply pass needle through the small hole and attach in a position around the area you wish to hit (eg. treble 20)
If any other sizes are required leave a comment and I'll try my best to update the f