The Burris 2-Piece XTB Xtreme Weaver-Style Solid Steel Base is able to fit either Picatinny-style or Weaver-style rings. These bases are hand polished and carefully inspected to ensure you get the highest quality. They are comprised of solid steel and precision machined. These Burris 2-Piece XTB Xtreme Weaver-Style bases are constructed to offer the highest level of flexibility for your rifle mount as well as stability. Attaching these platforms are easy and taking them back off is not difficult either.