I have to use 2 infant car seats right now and the carrier bases are putting a little indentation into the leather at 2 points for each carrier (not sure why they designed these gracos with these slightly protruding edges). I am thinking about adding a foam piece to the carrier bases themself to keep this from happening. If this protective cover is not thick, I'm thinking this problem would exist for you too unless it's a different design.

At any rate, I'm not a fan of covering up the seats entirely. (You won't need to worry about spills really - at least not at this stage - infants right?).

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'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr