Compatible with the Glock 17/19/19x/20/21/22/23/25/31/32/45. Not compatible with Gen 1 or 2 Glock models due to lack of forward Glock universal accessory rail. Can be used with a huge array of slide mounted optics. No longer is the MCK slide and serration dependent! Utilizing the NEW GEN 3 Charging Handle, you can use any aftermarket slides, sights or optics inside the MCK. More GEN 3 specific options and accessories coming soon! The GEN 3 Includes the NEW CAA USA GEN 3 Charging Handle!