I'm putting a set of the Carlisle HDs on my trailer the next time I pull it out. I talked with the manager of the local Discount and he wasn't aware of the difference, so he did some checking for me. He said that the HD is a tire specifically created and sold at Discount. Not sure, but I would assume that if it was rolling out everywhere, it would be on Carlisle's site. Anyhow, he said they mount a LOT of them (usually have 10-12 in stock) and he runs them on his TT. Hasn't had any problems with them in the past few years, and sees very few of them come back for repair.