The Align Tactical® THUMB REST TAKEDOWN LEVER is compatible with all HK® VP9/VP40/SFP9® standard and long slide pistols (Not specifically designed for VP9SK® Sub-Compacts but is capable of installation). Hardened S7 tool steel part finished in Black Oxide. Approved for USPSA Production. Made in USA with lifetime warranty.

*Holster selection requires clearance for extended ledge. Refer to Align Tactical's Compatible Holster Manufacturers for select models from Black Scorpion Gear, Werkz light-bearing, Long's Shadow Holster, Red Hill Tactical, Lynch Holsters, and Lytton Custom Holsters.  

https://www.aligntactical.com/products/hk-vp9-thumb-rest-takedown-lever