This is Novak's replacement Ballistic 550 Motor Hardware Kit (#S5933). For use with all Ballistic 550 brushless motors, and can also be used with HV-style 550 brushless motors. 

Each Kit includes:

Three 4-40 x 2.5” Socket Head Cap Screws 
Three M2.5 x 10mm Flat Head Cap Screws 
Two 5.1 x 7.5mm x 0.15mm Shim Washers 
Two 5.1 x 7.5mm x 0.25mm Shim Washers