That is a great question. We do have a customer who is a large car rental agency, and they uses these markers on their lot for a couple of reasons.
1. White marker shows up much better than color markers. White shows up better in all weather conditions and on bright days colors tend to blend into the sunlight.
2. You do not have to use a razor blade to take this marker off your car window, you just need to mild detergent and wipe if right off.
3. It glides on the glass. Making it very efficient and quick for them to write their notes on the glass.
Our customer also mentioned that they liked the next day deliver, they can call in their orders to our live US based customer service and they got a nice deal on the markers to boot.