840H owner, upgrade to Transformers can be used with the following kit:

840H Transformers-Y6

Hexa-rotor Y parts list:
840H CF Central Frames(Transformers) x1 pack
840H-Folding Landing Gear (Transformers) x1 pack
840H CNC Motor Mount Set (Transformers) x2 pack

840H Transformers-X4-E

Quad-rotor X parts list:
840H CF Central Frames(Transformers) x1 pack
840H-Folding Landing Gear(Transformers) x1 pack

840H Transformers-V6-E

Hexa-rotor V parts list:
840H CF Central Frames(Transformers) x1 pack
Recommended to use:931066-840H-Folding Landing Gear (Transformers) x1 pack

840H Transformers Manual Download
840H Folding Landing Gear (Transformers) Manual Download