The Saf-T-Blok 70111 Right Handed Safety Block is compatible with Glock Pre-1998 models 17, 19, 20, 21, 22, 23, 24, 26 & 27. Calibers 9MM, .40 S&W, .357 SIG & .45 ACP. Right hand model, fits all PRE-98 Glock pistols without finger grips and rail (FGR) Except M/29 and M/30 SAF-T- BLOK slides behind the trigger, snaps in easily and stays firmly in place thus preventing accidental discharge. SAF-T- BLOK is quickly ejected by the trigger finger. Independent tests by Performance Shooting, Inc. showed that "0" time was added to draw and fire the weapon. Highly recommended for unconventional carry. Suggested use when carrying in a fanny pack or tucked in the belt, etc. When installed, goes unnoticed and can prevent your own gun from being used against you during a gun snatch. Comes with Pre Drilled through hole to allow a user to install a small key lock for when firearm is being stored. Available in black only. WILL NOT WORK WITH AFTERMARKET TRIGGERS. Concept Development Corporation designs and develops unique products for Law Enforcement, the U.S. Military and the Shooting Sports Industry. Their products are in use worldwide.