Proprietary design maximizes internal length allowing for extended cartridge overall length of 3.9 for all of Seekins’s long-action calibers. The hand-laid carbon fiber body provides extreme durability and weight savings(total weight:1.4oz). Always be ready with a backup and order your spare mags today. *7mm Rem Mag 28 Nosler .300 Win Mag 300 PRC 338 Win Mag *These magazines will only work with proprietary HAVAK PH1 and PH2 DBM and are NOT AICS compatible.