Step four - assembling and installing the hub shifter interface on the Nuvinci was challenging, mainly just because I'm not very good at following instructions. I couldn't get the hub interface (where the control cables hook up to the hub) connected properly, and I ended up breaking it in the process. So I tried every website I could think of for replacement pieces with no luck, until I eventually called Fallbrook Technologies directly and spoke with a rep named Mia - I explained what I had done, and she just mailed the new pieces to me, no charge! What a cool lady. Anyway, take the time to read the instructions before you get too "energetic" with your installation. If you do break something, use this parts catalog (http://www.fallbrooktech.com/docs/Parts_CatalogV5.pdf
) and just call them directly to order.