I dont like to disagree, but HTD means High Torque Drive....when applied to a synchronous belt, AFAIK the mountune belt has a different cord material, one used for higher engine bay tempertures experienced on the Grp'a' and wrc cars with ALS etc....

I have had some dealings with both the standard and mountune belts, even to the point of analysis with gates when we had 2 failures on rallies using the standard belts. We now dont use anything other than the mountune item.

That said under normal road even mild track conditions, the cosworth belt is quite adequate....in my opinion...