Sierra Bullets has collaborated with Sig Sauer to introduce a premier line of defense bullets, offering optimal weight retention and expansion across all effective distances, coupled with Sierra renowned accuracy. This line features a stacked hollow point bullet design with an additional hollow point cavity. For models #9924, #9925, #9465 and #9820, a cannelure positioned midway up the shank secures the jacket to the core, ensuring maximum weight retention and terminal expansion. Model #9924 was launched in November 2015.