The Short Action Customs Modular Headspace Comparator Insert is an updated version of the highly successful dedicated Headspace Comparator that SAC previously made out of 6061 aluminum. Short Action Customs improved on its design allowing the MHC to be used with cartridges up to 338 Lapua Magnum and more. Each bullet and headspace insert is precision machined out of 17-4 Stainless Steel for increased durability and corrosion resistance.Features6061 aluminum