Absolutely fantastic model, great fun to build and interesting to see how each of the functions has been implemented, especially the collective levers, which alter the angle or pitch of the rotor blades. If you can afford it, it's worth getting the power functions kit. You can actually feel a down draft from the blades when they're angled - it's not much, but first for any Lego helicopter I've owned! :) I let my nephew have a play, under very close supervision (he's only 2.5), and he was amazed. Kept his attention for quite sometime, which is quite a feat in itself!! :) He did want to make a few changes to the design, notably removing the tail fin on more than one occasion! :D This is a great model, good size (i.e. big!), quite complicated to build, so interesting, and lot's of fun. Thoroughly recommended, another hit Lego!