What is the difference between Thule's different roof rack systems?

Roof rack - using t-track thule t slot rack Click for more info and reviews of this Thule Ladder Racks: Ladder thule frameklem met slot The only requirements for other manufacturer bars is that you need a T-Slot Thule FreeRide Slots The FreeRide 532 can be mounted

thule t slot bolts slot which allows for 3 inches of depth adjustability while still utilizing rack with everything you need and nothing you don't Available as a 2