This is a perfect tool to consistently mark where on your shaft you're going to put tape-on fletchings,.
It fits most of vanes on the market, such as Spin  Wings, KSL Jet 6,  And all arrows up to 7.2mm diameter (9/32in) Nock-Out-Diameter.
 
Gasprom Spider.  Clamp your arrow in place, and then mark on the shaft where each vane should be placed.

• Used to mark exact vane location on your arrow shaft
• Works great for spin wing type vanes such as: Spider, Kurly, and XS Wings