When it comes to training indoors, the Kreitler Challenger 4.5 Rollers with Killer Kool Headwind Fan are without equal in improving your spin, balance and form. The Challenger 4.5 Rollers use the same 4.5 inch machined aluminum drum cylinder as the Alloy 4.5 Rollers, but use Poly end caps for a more economical option. Kreitler drums are made from high quality aluminum, lathe-turned to within .002" for smoothness, and anodized for a long-lasting finish. They spin virtually without resistant on instrument quality bearings. The Kreitler Challenger 4.5 Rollers features 4.5 inch alloy drums with polycarbonite end caps and 15 inch roller frame width. The included Kreitler Killer Kool Headwind Fan is an adjustable resistance unit that runs off a belt coming from the front drum of your Kreitler Rollers. Lifetime warranty.