Titan package T4-B2 includes (2) heavy duty flat belts specifically designed to work on Titan T4000 & TC6000 upright vacuum cleaners. These belts are made from a better rubber compound and are wider to insure long life and consistent brushroll speed for better performance. We recommend changing your T4000 or TC6000 belt every 6-12 months with the T4-B2 flat belt to insure proper brush speed. Even if you don't believe the belt is worn do not let your belt go more than 12 months. These belts are friction driven and the constant tension causes the belts to loosen over time.