I think that's mousse, the enduro x bikes on you tube and guys I ride with on mousse cut down to "volume" ( think 6psi) look the same when you follow them, and they grip everywhere. They cut a section out of a new mousse ( maybe 6 to 8 inches out) and it still neatly fills the tire, they add bits of the removed section as the tire "feel" gets too low. they don't dent rims. Expensive but it looks like it works.