Headspace Inserts for your Modular Headspace Comparator ***Requires Modular Headspace Comparator Body*** The Modular Headspace Body must be purchased separately and can be found at the Modular Headspace Comparator Body page. New Modular Design for the most accurate cartridge headspace and bullet measurements available! Newly designed Modular Headspace Comparator (MHC) is an updated version of the highly successful dedicated Headspace Comparator that SAC previously made out of 6061 aluminum. They improved on its design allowing the new MHC to be used with cartridges up to 338 Lapua Magnum and more. Each bullet and headspace insert is precision machined ou Mfg: Short Action Customs