From Bbmykal:

“Okay they are not cheap, total was something like $120.00 but I need to maximize my MINI's boot.

The bags go under the rear shelf and attach with 4 screws provided. There were places for the screws to attach to already on the shelf (I never noticed the four little bumps). It has the “offical” Owner's Manual holder on the left, a wide pocket in the middle (holds my Gtech, screwdriver, and trorx driver) and a small pocket on the right with the MINI logo (holds 2 FRS radios perfectly). You can tell how deep the pockets are as it's only as deep as the shelf itself. When I originally purchased it from the pictures in the catalog, it looked like they hung off the back of the seat (thus the name “saddle bags”) but no it's totally held on under the shelf. Works nicely when those string things are attached…

For those interested the official MINI part number is: 82 11 0 154 464