Toughest tube Michelin makes, engineered for hard enduro, rally raid, and the most demanding off-road conditions. Walls are thicker again than the heavy duty version, with the Airstop butyl compound carrying through for best-in-class air retention even at the bigger gauge. The right choice when running very low pressures over sharp rocks, racing where a flat ends your day, or riding remote routes far from any chance of a roadside repair. Heavier than the heavy duty option, so a clear unsprung weight trade-off, but the durability gain is the point. Pairs naturally with aggressive enduro and rally tyres like the Mitas Terra Force range or rally-spec Pirelli Scorpion Rally. Available in sizes matched to common front and rear off-road and enduro tyre fitments.