Use Weaver-Style Rings On 3/8" Dovetail Receivers Lets you choose from a wide selection of Weaver-style rings for receivers with nominal 3/8" dovetail. Secure, single-slot, two-piece design allows perfect ring spacing every time and easy access to chamber. Made of aluminum to keep weight increase to a minimum. SPECS: Aluminum, black matte finish. Each base measures 1½" (3.81cm) long.