GG&G's website only mentions Streamlight flashlights in their product description and that is why it threw me off:
https://www.gggaz.com/hk-usp-picatinny-rail-flashlight-mounts.html
HK USP Flashlight And Laser Picatinny Rail Mount Specifications:
Easily installed.
Picatinny (MIL-STD-1913) dovetail rail mount for lights prepared to mount on this style of dovetail.
Fits Streamlight TLR-1, TLR-2 and L3 / Insight M3 and M6.
Fits tightly to the USP trigger guard allowing for the rear rocker switches to be activated by the fire control finger or thumb of the off hand.
Three piece, lightweight mount easily clamps onto the existing USP light rails.
The rail fits tight enough to retain zero on laser sights.
Materials: Manufactured from solid billet 6061-T6 aircraft grade aluminum.
Finish: Type III hard coat anodized matte black per Mil-Spec.
Weight: Full Size: .70 oz.
Compact: .65 oz.
Warranty: Lifetime.
Made In America By Men And Women Proud To Be Americans.