Standard Timing Belts - XL, L, H, XH, XXH. Trapezoidal Tooth Profile (Oil, Heat and Abrasion Resistant). Stock timing belts are listed below. They have fiberglass tension members, chloroprene body with nylon covered teeth, all bonded together for maximum strength. Jason timing belts are specified by belt length in inches times 10, belt pitch code and a three-digit belt width code, which is the decimal inch-width multiplied by 100 - Example: 240L075.