Kit to stretch the N556 to a 600 size.
1 each 556-034 34t Helical Tail Drive Gear
1 each 556-014 14t Motor Pinion
1 each 556-414 N556 Stretch Torque Tube
1 each 556-412 N556 Tail Boom Light
1 each 556-410 Tail Pushrod 595mm
This kit plus blades is all that would be necessary to stretch a new kit when building.
If stretching an existing kit you will also potentially need:
Of course main and tail blades would need to be purchased.