There are better options - Hawke Sport Optics Picatinny /Weaver Rail Adapter - 2 Pieces. 9-11mm

What a joke. This was purchased for a rifle with a 9mm dovetail over the barrel and 11mm dovetail over the receiver. The dovetail adapter didn't fit the 9mm rail, it was too big even when tightened fully. It fit the 11mm dovetail, but the clamp for the dovetail doesn't have enough vertical separation from the Picatinny rail, and interferes with mounts attached to the Picatinny rail. Picatinny scope rings fit awkwardly with a significant gap against the clamp side, and my QR mount wouldn't even fit over the Picatinny rail, as the clamp blocked the mount from interfacing properly. I would return it as defective, but for the $30 it isn't worth the hassle.

I have similar adapters by UTG and SunOptics (both purchased from OpticsPlanet) and both of those mounts have far superior fit and finish and have never given me problems with properly fitting the dovetail or Picatinny mounts.