Standard Losmandy-style D plate. This plate is 13" long. For mounting Stellarvue rings with two screws the ring spacing will be 8 1/4" - 9". Mounting with the center screw only the spacing is quite variable from 2 1/2" - 10 1/2". The plate includes multiple countersunk and threaded holes with 1/4-20 and 6 mm threads. Dual safety screws on either end may be used. Each plate comes with two safety screws and four 1/4"-20 and four 6 mm socket cap head screws for ring mounting. Make sure you select the proper thread screws to avoid ring damage.