Q: Will any iPod touch third-generation case work for my third-generation 8GB iPod touch? Or are the sizes of an 16GB and an 8GB model different?
A: The short answer is yes. The second- and third-generation iPod touch models were identical in terms of physical design, with the only difference being the internal hardware components.
It is worth noting, however, that there actually is no “third-generation” 8GB iPod touch. In 2009 the third-generation iPod touch was released only in 32GB and 64GB capacities while Apple continued selling the previous year’s 8GB second-generation iPod touch as the lower-end model, similar to what Apple has done with the iPhone 3G/3GS and iPhone 3GS/4. The 8GB iPod touch model was only available in the original first-generation, the 2008 second-generation model, and the most recent fourth-generation model released in 2010.