lewisnoble here!! In the forum as lewisjnoble.
The Marathon XR I am selling are probably best described as heavy duty touring tyres, now replaced in the Schwalbe lineup with the Mondial I think. The XRs had a reputation for being very strong and puncture resistant - I doubt if anything is puncture proof, but the Xrs are syupoosed to be as near that as you can get.
See my post in Bike Bits for Sale.
By the look of them, the Extremes are more for heavy duty off road touring?
Lewis 07980 202830