I'd be terrified to take my box through the car wash.
BTW, you can get the new and better quick release models in the USA for cheaper. That price is horrible for only 11cf. Just strap it on and drive back.
EDIT: I just checked some pricing and it seems that Thule have raised the US pricing instead of lowering the Cdn pricing, interesting. I take back my pricing comment. Its not horrible, just not as good.