not a dumb question at all...i had no idea until I investigated either
The upper pillow mounts replace the stock damper mount and factory strut bearing with an aluminum mount and metal strut bearing. By replacing the softer factory damper mount and rubber strut bearing with metal components, vehicle handling and response become more firm and precise.
In addition (to this info taken from
http://www.g-speed.com) the front upper pillow mounts on the Teins allow for camber adjustment, by adjusting the upper mounting point of the strut.
the pic below, shows the right Pillow mount (front) with the slot in the middle for the camber adjustment. Notice the rear is just a hole, with NO camber adjustment.If you DO decide to get pillow mounts from another company for Tein struts, MAKE sure the strut will fit into the mount, b/c the sizes are NOT universal