The Pro Mod drag racing division has specific rules about engines, components, bodies, etc. Usually, the IHRA races Pro Mod cars on the 1/4 mile, resulting in low-to-mid 6 second passes, while the ADRL races strictly on 1/8 mile track setups, allowing for high 3 second-to low 4 second passes. Pro Modified has only been around for about 15 years, whereas other classes are much older. Despite Pro Modified cars being slower than the Top Fuel or Funny Car classes, it has become one of the most popular divisions of the sport. The Pro Modified division was a spin-off of the IHRA's Top Sportsman division but with fewer limitations, allowing for significantly higher performance. The American Drag Racing League's top three classes (Pro Extreme, Pro Nitrous, and Extreme 10.5) are comprised of all Pro Modified vehicles, making the ADRL one of the fastest growing and most popular drag racing organizations. Due to the near-limitless engine/drivetrain combinations and incredibly lenient rule system used by most Pro Modified racing organizations, competing teams in this series of drag racing have virtually every freedom to make their car as fast and competitive as it can possibly be.