Eliminates variations in bullet seating depth by measuring ammunition from the ogive. Comparator attaches to any caliper and can measure cartridges from .17 to .45 caliber. Comparator inserts sold separately or in set. Comparator Set: Contains the B-2000 Comparator and 6 inserts in a plastic storage box. Insert calibers .22, 6mm/24, .25, .270, 7mm, .30.