That's a loaded question.  Disc brakes, second mirror, rack, panniers (Arkel ), front/ lighting system, spare tube & tire, hydration system (FastBack), etc.

 

Clips/bike shoes are a must. My foot came off of the pedal when I hit a bump. Then my foot touched the ground and I ran over my lower leg when the axle hit the rear of my leg.

 

A fairing (Windwrap) is a nice option but not a must.

 

Most of these items are listed on Greenspeed's web site: http://greenspeed.com.au/links.html

 

 

Since the X5 folds I assume you don't need a car rack for transportation. But it you do, consider these guys: http://hitchrider.com/trike-rack.htm

 

Have fun!!!

 

Craig