The Alloy is the top-of-the-line when it comes to rollers. The all aluminum drum construction, aluminum end caps and shield bearings are perfect for high rpm continuous pedaling. The drums are 4.5" x 15" and perfect for use with the "Killer KOOL Headwind" and Flywheel. The Alloy has a black epoxy powder coated frame and an orange belt. The Standard Kreitler Frame is adjustable for wheelbases from 31.5” to 48.5”. This set of rollers comes with the "Killer KOOL Headwind." The Killer Kool Headwind Fan is an adjustable resistance unit that runs off a belt coming from the front drum of your Kreitler Rollers. The Headwind Fan has several functions. The main function is to add resistance. An adjustable air inlet controls the amount of resistance desired. When closed, the additional resistance is minimal. Wide open, the resistance is high enough for even the strongest riders. The second function is to provide a cooling breeze. The Fan unit can be rotated to point the airflow high or low, and adjustable louvers can fine tune the side-to-side direction. Staying cool will make your workouts more enjoyable and is less stress on your body. The Fan attaches to the front left side of the Frame. You can also direct the airflow away from you if desired.