Two-Piece Ring Mounts are made out of high grade aluminum and hardcoat anodized; with hex nuts to fit picatinny rails in spec or out of spec. Featured Upgrades For 2nd Generation Lightweight lever or hex nut system Weight reduction up to 35 g / 1.24oz Same durability guaranteed NEW: T5 (GEN-2) – Hex Nuts ALUMINUM Clamping Jaw Steel hex nuts (like T2) in combination with a clamping jaw machined from high-grade aluminum allow for a weight reduction up to 35 g or 30% depending on the respective product. These new hex nuts come with a special, self-locking thread which reliably prevents vibration-induced loosening. ERA-TAC ERATAC Gen 2 Two-Piece Ring Mount Nut 34mm 35mm-1.38" High T5004-0018