I have 5 black Prince Lionheart seat savers and 2 bubble bums for sale. I can split up or sell as a group.
Amazon has the prince Lionhearts for $21 each and bubble bum's for $28 each. I'll sell for half of that plus shipping.
The Lionhearts are must have if you are planning on using booster seats or car seats and don't want your seats damaged. I used them in my e46 since day one and didn't have a single mark on the seats. I then bought an e90 from an owner who didn't and almost 2 years later the car seat indentations are still visible.
The Bubble Bums are necessary for booster seats. The normal booster seats simply won't fit in the M3. Both work, but one requires a little air once in a while due to a slow leak. It only takes a second though and needs no tools, so it's really not a big deal. They are also great for vacations as they deflate and pack very easily...very convenient for air travel.
http://www.amazon.com/BubbleBum-Infl...rds=bubble+bum
http://www.amazon.com/Prince-Lionhea...art+seat+saver