I booked an SUV from the Karlsruhe Knielingen 24h branch for my trip on 16th of December. Everything went smooth upon the car handover. SIXT had upgraded my car category to a brand-new Audi Q3. The car was clean and the handover took 5-10 minutes. Everything went also smooth upon the return of the car. Until now, no surprises with extra charges. I do recommend this branch.