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I just picked this up at wal-mart. It fits great in the Model S, covering the entire windscreen. It reaches all the way up to top of the small sun visors for a secure fit. It only cost $10.97
I purchased a few years ago and the split one was all that was available. I've used the single roll in other cars, and the only issue is that there are no stiffening rods so over time it sags. (I just put a small box on the dash to keep it close to the window.)