another T5 lighting question

[lagatbezan]

I was looking at the Tek T5 lighting and was wondering if someone could explain the difference between the retrofit kits and the ready fit kits.
I have the links below:
http://reefgeek.com/products/categories/lighting/104067.html
http://reefgeek.com/products/categories/lighting/104932.html

thanks in advance.

 

[s3aL]

Basiclly the ready fit retrokits are for lazy people who want to just be able to screw it in the canopy without having to do any messuring or lining up .