Carbon steels just seem to polish best with a genuine Arkansas stone and the four shapes in the kit have proven to be the most useful in the gun shop. The edges are nice and clean, making them an excellent choice for flat trigger and sear faces plus most other gunshop fitting chores. Fine cut, white hard Arkansas. SPECS: Set includes - 1/4' (6.3mm) x 4' (10.1cm) Triangle; 1/4'
x 4' Square; 1/4' diameter Round; 1' (2.5cm) x 4' Knife tapers
from 1/4' thick to 1/16' (1.6mm) thick.