These are the scale retract units designed specifically for the Top Flite P-51D Giant Scale. This unit pivots on the outside of the unit. The hinge point is on the front of the retract unit. FEATURES: Fully functional Oleo Strut. Offset Axles to provide a scale wheel stance. Glass filled Nylon Frame with Aircraft Steel and Aluminum with Positive Up and Down Locks. SPECS: Width of retract unit: 2.5in (64mm) Length of unit: 2" (53mm) Diameter of Strut wire: 1/2" Weight Bearing Capacity: 22 to 24 pounds. Weight per pair: 23.2 oz. REQUIRES: 1 ROBQ2367 1 ROBQ2368 1 ROBQ2369 1 ROBQ2392 Also Requires Tee-Fittings (1/16") ROBQ1635 and Retaining Nuts Recommended that 5" Wheels are the Maximum size that can be used. INCLUDES: Axle hardware to mount the wheels to the retract struts. COMMENTS: This unit is recommended only for the Giant P-51D Mustang from TF.