Cooper Discoverer ST Maxx Mud Terrain Radial Tire - 275/70R18 125Q Tire Only Armor-Tek3 carcass construction contributes to the durability of the S/T MAXX by adding strength to the sidewall and tread area. Blended natural rubber and silica based provides exceptional wet traction and confident handling on the highway, while also delivering excellent cut and chip resistance on unpaved, rocky and gravel terrain. Stone ejector ribs help to discharge stones and resist stone drilling. Enhanced buttress design provides additional off-road traction, abrasion and puncture resistance.