This is a genuine Electrolux Versatility / Oxygen Upright Vacuum Cleaner Serpentine Belt for Electrolux EL8500 Versatility Upright Vacuum, as well as the Sanitaire SC9180, SC9150 Uprights.  This is what's called serpentine or grooved belt, which has grooves on the inside of the belt.  Electrolux / Sanitaire Part Number 77133. 1 Belt Per package.