The iPod classic replaced the 5th-generation iPod in September 2007, acting as a 6th generation of the original (hard drive) iPod line. The first revision had two models (as many generations of iPod before had had) with 80 and 160 GB of storage. (Typically, the smaller-sized model was thinner because its hard drive had one rotating platter instead of two.) An update a year later merged the two models into one 120 GB model. This model was the physical size of the previous 80 GB model. In September 2009, the iPod Classic was updated yet again to a single platter 160 GB hard drive.