Forster Co-Ax Primer Seater W/ E-Z-Just Shell Holder Jaws There are other primer seaters on the market, but none quite like our exclusive Forster Co-Ax Primer Seater. Unlike other seaters, ours is designed so the operator can eliminate all slop when working with a specific cartridge. That translates into perfect seating, reliable ignition and reduced misfires. No additional Shell Holders are required. The E-Z-Just jaws close to securely grip most modern rifle and pistol cases with a rim thickness of .045" to .072". Other features include a built-in primer flipper tray. Large and small primer tubes have an open slot and primers stack sideways for added safety. (Small holds 52/Large holds 41)