Mice can get through a 1/4 inch opening or less sometimes. I have a dozen mousetraps with peanut butter around my SL. and check constantly for activity. The little bastards are persistant and you just have to be smarter than they are. Insurance should take care of any damage.

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95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K