A graduated syringe and some rubbing alcohol will tell you very quickly. Make sure what
you're measuring is flat, put a measured quantity in the syringe (available at veterinary
supply places), fill the area to be measured till it JUST comes out, read what's left in the syringe,
and do the math. Very helpful to know how to do this, works for heads as well and
allows you to cut them yourself and get them both the same. 6" tabletop belt sander works good
for cutting the heads down-thanks Paul!