And to add to that - if you don't wish to wire the flexwatt yourself (I personally don't) - you can specify that you want, for example, Qty 5 - 1 foot sections of 11" flexwatt wired. Or Qty 5 - 2 foot sections of flexwatt wired. (I order from Rich at Reptile Basics as well).
So you'd order the total number of feet you need, then add in your comments to your order - be sure to buy the clamps needed to wire as well and then he'll wire it for you for free.