it's a sun shade that resides in the back window. A luxo option standard on most 7 series e38s (and maybe later year e32's? I don't know, shogun would) in the US. I guess it'd be good if you've got occasion to cart around heads of state and what not, or if you just want to protect the leather seatbacks a bit more from the angry sun....but, from my perspective, I'm always in the driver's seat, so it doesn't affect me, and I rarely have passengers.

best, whit