Within every Remington primer is a group of subcomponents assembled to exceptionally tight tolerances. Primer cup dimensions are controlled to .0001″, and the priming mix is specially formulated for consistent ignition with a wide variety of powder types. Remington sts 209 primers are tested for reliability from -20 degrees F to +150 degrees F. The unique tripod anvil design creates a larger strike area with maximum sensitivity, even with off-center firing pin strikes.