he says "D" series at 1:40
Then, when I started watching this video, them mention testing it out at the Delta Plex. Thats an old Hockey/Concert arena that is about 10-15 minutes from where I grew up and actually where my graduation ceremony was for High School. They later mention the dunes specifically.
That's really awesome. I wish there was more press about the Dunes in Michigan. They're an absolute blast. I'm hoping to take my Taco there next summer with my new 4-wheeler (still on the yet-to-be-purchased list). I haven't been out there in either a truck or on a 4-wheeler in years.