Question: what is the difference between the apple series 1 and 3?
Answer: Series 3 with LTE has a ceramic back covering its heart rate monitor and other sensors, while the Series 3 with GPS and Series 1 have composite glass backs. Series with LTE also has 16GB of internal storage for storing more apps, songs, and images, whereas Series 3 with GPS and Series 1 have just 8GB of space.