Originally Posted by Russ Roth

Looks like a fat dry weather or grass cross tire which is probably what it really is.

Seems that with official cross tires capping out at 33c, though I've never heard of anyone having an issue with wider, gravel tires seem to cover that gap from cross to mtb sizes. Most look to me like fatter cross tires, the ones Challenge produces even seem to be the same tread patterns with a touch more puncture resistance and more width which is fine. Having toured with my gravel bike I was happy with the 38c gravel tires I picked which aren't too heavy, strong enough to not flat even once yet, and offer plenty of traction on the packed gravel rail trails that most of the tour followed while offering a decent level of speed once I hit pavement. Seem bike a valid tire designation to me.