Retainer Assembly, 54mm, L2 Two-Piece Light-Weight Assembly For 54mm Motor Mount Tubes `L2` (for 2.242" OD motor mount tubing) Precision Machined 6061-T6 Aluminum With Mil-Spec Type II Black Anodizing Large Quick-Turn Threads For Fast, Tool-Free Motor Change Installation: Simply Bond To Motor Mount Tube With JB Weld® And You`re Done! Just Slide Motor In And Thread On Cap, That`s It! Can Be Installed On Existing Rockets With Motor Mount Tubes Extending 1/2" Or More Below Lower Centering Ring (Aeropack)