This is a good replacement for your 500 class Helicopter
500 Class Tail Boom (Belt Version)
500 Class Plastic Tail Blade (76mm from bolt hole)
STASRC 500 4Blades Tail Rotor Holder for TREX Align 500 Helicopter
Trex 500 Autorotation Tail Drive Gear: Tarot 500 TL50019
500 Class Drive Gear Set
500 Class Flybar Head Linkage Rod set
