Add extra precision to your arrow builds with this squaring tool from Carbon Express. 

Comes with three sizes to suit

Hunting (Standard)
0.244 (Maxima size)
0.204 (Maxima SD)
0.166 (Nano 166, ACE size)

Competition Edition (Target)
0.318 (X-Buster, Tank 23D)
0.349 (Tank 25)
0.378 (Tank 27)