Internal fiberglass tensile cord provides flexibility, usage life, resistance to elongation and high torque strength.D270XL001 DAndD Powerdrive XL Double Replacement Timing Belt Of Teeth: 135, Material: Neoprene, Series: XL, Pitch: 1/5 InchFEATURES And BENE FitsPrecision-formed trapezoidal or squared bottom elastomeric teeth on both sides of the timing beltDual timing belts provide equal load carrying capacity from both sides of the belt.