Can I use my old AirPods protective case on AirPods 2?

Yes, your old case will fit AirPods 2, but...

AirPods 1 and 2 have identical dimensions. So the wired and wireless charging AirPods 2 can fit into your old AirPods case. The only downside is that the LED indicator of the wireless charging AirPods has been moved to the front, so it will be covered by your old protective case.

That’s cool. Should I upgrade then?

It depends if you really need the new features. The new version now supports hands-free “Hey Siri” functionality. It is a convenient feature for the user to control volume and song playing with voice command. Another upgraded feature is the updated H1 chip that supports Bluetooth 5.0. It provides faster switching time among your Apple devices including iPhone, Apple Watch, iPad, Apple TV, iPod and Mac.  

Are AirPods 2 backward compatible with my old AirPods?

AirPods 2 actually come with two versions - wired charging one and wireless charging. You can get the new AirPods without the charging case for US$159, with the Charging Case for US$199. And yes, the AirPods 2 charging case is backward compatible with old AirPods. So if your original charging case is not working anymore or you simply want to upgrade, you can buy just the Charging Case for your existing AirPods for US$79.