Brownells Extra Power Magazine Spring Fits Smith & Wesson M&P

The extended magazine spring is designed to replace the factory-supplied spring for compatibility with aftermarket magazine extenders and extended base pads, thereby increasing the magazine's round capacity. It provides the follower with up to 10% additional power, ensuring smooth and reliable feeding of rounds. Constructed from certified aerospace-grade chrome silicon wire, the spring undergoes heat treatment and stress relief in accordance with ISO 9000 standards. Compatible with Smith & Wesson M&P pistols, accommodating calibers of 9mm, .40 S&W, and .357 Sig