The Durano Plus has a belt of protective Smartguard rubber under the tread, as used in Schwalbe’s virtually impregnable Marathon Plus touring tyre. This is why the tyre is so heavy, why it’s such a pig to fit (we had to use toe-straps to grapple it on), and also why it shrugs off sharps like a solid rubber ball.
The sidewalls are pretty hard to cut too. You’d expect a tyre with this level of imperviousness to roll dismally slowly or scrabble for grip like a solid tyre. Not so. In our tests it was mid-pack. Our experiences with Marathon Pluses suggest its mileage should be excellent too.