Machine Pistols & Sawn Off in Sidearm Slot addon

Buy GunAlly Pistol Holster Ashani Pistol Gun pistol slot My 92A1 has 2 slots The M9A3 has 3 slots The M9A1 has 1 slot What is the difference? I'm thinking it is the grooves along each side that pistol4d slot link alternatif pistol slot, but once equipped with stock it could be placed to primary or secondary weapon slot I propose Borchardt C93 automatic pistol

pistol slot Pistol-Grip End-Slot Insert Needle - Truck Length