Style "U" Eureka Sanitaire Belt For use on 2900, 2920, 2970, 4100-4600, 4700, 5180-5190, 5700-5800, 7600, SC4570, SC4580, SC5713, SC5745, SC5747, SC5815, SC5845, SP5816 and 9000 series. Belts are rubber and will stretch and wear out. The belt turns the brushroll at thousands of revolutions per minute. The tighter or newer the belt, the better the vacuum will perform. So, it is important to check the belt periodically for any signs of wear that can result from normal use over time. For optimum performance, change your belt at least every 6 to 12 months.