The RCBS 338 Lapua Magnum Precision Mic is an essential reloading tool that enables precise measurement of chamber headspace and bullet seating depth to 0.001 inch accuracy for safe accurate ammunition loading.RCBS 338 Lapua Magnum Precision Mic (SKU: RCBS-88332)Measures chamber headspace and bullet seating depth to 0.001-inch precisionMeasures from datum point on case shoulder to base for SAAMI tolerance readingsEasy operation with just a few twistsHelps create safe accurate loads that extend brass lifeThis indispensable reloading tool ensures consistent safe ammunition by providing spot-on SAAMI tolerance measurements making it essential for serious rifle reloaders working with 338 Lapua Magnum cartridges.