Safariland 6360 Level III ALS Retention Duty Holster, Mid-Ride, Black, STX Tactical, Glock 20, 21 Automatic Locking System (ALS) secures weapon once holstered and easily releases with thumb when initiating proper shooting grip SLS (Self Locking System) adds an additional level of retention Weapon specific thermomolded outer is suede lined to protect the weapon's finish The #6000 hood guard is standard Comes standard with a 2.25" belt slots with retention nuts