The Specialized Chunder DH has a 2 ply casing & Butyl stiffened sidewalls making them super stiff. Adding to the impenetrability of the tire is the 60 TPI casing. All of this makes the downhill version of the Chunder extremely tough; it is near impossible for thorns to go through & pop your tube. The Chunder DH wears very well too; even when riding on very rocky terrain these tires lasted a long time before needing to be replaced. Specifications:&8226; Casing: 60 TPI&8226; Center Compound: 42a / Shoulder Compound: 40a&8226; Dual ply casing&8226; Butyl stiffened sidewalls&8226;26&8243; x 2.3 approx. weight 1350g PSI: 25-50