Product Features Fits the Smith & Wesson 9mm M&P (does not fit the single stack S&W M&P Shield). Extended 21-round capacity Base plates interchangeable with ETS line of 9mm double stack magazines Due to the wide variety of extensions for Glock, the mag base is designed to be compatible with Glock extensions Easy disassembly with the specially designed base plate Ergonomically designed floor plate makes it easy to grab from mag pouches Lifetime Warranty Product Specifications Manufacturer: ETS Model: Smith & Wesson M&P 9 Caliber: 9mm Magazine Capacity: 21