1 chainwheel kit: 

This kit will work with your bike's rear gearing system.  You can enjoy the high-end cruising speed and also the low gear power for climbing hills.

3 chainwheel kit: 

If you are an active person, this is the system that you are looking for.   Adding to the 1 chainwheel kit, the 3 chainwheel set up will give you more room under the chainwheel for rock climbing or whatever you like to do.  It also has an extra 24T chain wheel to give you more climbing power.

Double freewheel kit: 

This kit will give the recumbent trike owner more power to enjoy mountain climbing, or cruising along the beach.