Retainer Assembly, 75mm, Universal (with flange) Two-Piece Light-Weight Assembly For 75mm Motor Mount Tubes Precision Machined 6061-T6 Aluminum With Mil-Spec Type II Black Anodizing Twelve 6-32 Stainless Cap Screws and Threaded Inserts Included Large Quick-Turn Threads For Fast, Tool-Free Motor Change Installation: Flange-to-Centering Ring Attachment, No Adhesive! Just Slide Motor In And Thread On Cap, That`s It! Can Be Installed On Existing Rockets With Minimum Airframe I.D. of 3.875" (Aeropack)