Designed for use in the Lock-N-Load Headspace Gauge, these bushings are machined to exacting tolerances to ensure reliable results every time you use them. The Lock-N-Load Headspace Gauge allows the reloader to precisely measure cases while sizing them for a perfect fit in any firearm. For use with the Hornady Headspace Comparator Provides the ability to check most bottleneck cases from .17 REM through belted Magnums Extend brass life improve accuracy and enhance safety All bushing are interchangeable with the Comparator Bullet comparator and calipers sold separately For D-.400"- 43 WIN, 7mm/08 Rem, 308 WIN, 7mm STE, 260 Rem