Right, A subframe mounted seat, means a seat, thats on a frame, usually allowing for sliding and tilting in the seats. Thats a subframe, as you can see, it allows the seat to move foward and backwards on the sliders. Side mounted bucket seats, such as the ones you posted, are bolted directly to the floor pan, via brackets. As you can see, the brackets are alread on there, and that just bolts directly to the floor.