This is the Locking Receiver Plate that makes it much harder to pull your holster off.
The QUICK-KIT includes the QLS 19 Locking Fork and QLS 22 or QLS 22L (Extra Locking Feature) Receiver Plate components. Constructed of injection molded nylon, the receiver plate can be attached at different angles according to user preference. The QLS (Quick Locking System) allows for quick transfer of gear between attachment points such as a belt loop, tactical leg shroud or other stable platform. The QLS fork and plate combination passes the Level I Retention™ pull test. Allows users to rearrange gear quickly and easily without the use of tools. Hardware and Allen wrench included.