The comparator attaches to any caliper and measures cartridges from 17 to 45 caliber. When used in conjunction with the Hornady Lock-N-Load OAL Gauge (sold separately) you will be able to determine the exact bullet seating depth.

Features:Comparator body;7 comparator inserts for the following diameter bullets: 224, 243, 257, 264, 277, 284 and 308 (others sold separately);Allen wrench