The Gen4 is based on a full size G17 MBS (multiple back strap) frame witha reduced short frame trigger mechanism housing. The multiple back strap system allows the user to change the circumference of the grip to fit their individual hand size. The grip has three options; a short frame version, medium frame or large frame that are easily changed and secured with a single pin. The grip angle of the GLOCK 'Safe Action' Pistol is not changed by back strap modifications. This ensures that the shooter does not shoot high or low when modifying the back strap or when shooting with a different GLOCK Pistol.