Originally Posted by MercedesSL600Man

If you enroll in the loyalty program, complete the pre-check-in, and also download the Sixt app, you are able to select a specific vehicle in your reserved class starting 30 minutes before your pick up time.

I've used it several times and it's pretty cool. Tells you the make and model, how many miles it has and how long it's been in the fleet, I believe.