When Amazon launched the updated version of the Kindle Oasis in October 2017, one of the headline features was support for Audible, meaning you can switch from reading to listening, thanks to Bluetooth hardware.
However, Amazon also announced at the same time that a couple of other Kindles in the family that offer Bluetooth would both be getting the update so that they can support Audible too.
The entry-level Kindle (2016, eighth-gen) and original Kindle Oasis (also 2016) both have the hardware in place and now the update is available, so you can make a Bluetooth connection to headphones, speakers or your car, allowing you play Audible books.
The inclusion of Bluetooth in these devices isn't something that's been widely acknowledged. In fact, Bluetooth isn't listed in the specs for the basic Kindle, but is in place to support one of the accessibility features - VoiceView. For the Kindle Oasis, there's no mention of it at all.
With the Audible feature enabled, you can sync any Audible books you might have. If you happen to have both versions of a book, then you can seamlessly switch from reading to listening. Amazon also offers a £2.99 special price on Audible editions, if you buy them at the same time as the Kindle book.
While the Audible update is a good thing for the older Kindle devices, it's worth remembering that both the Kindle and Kindle Oasis only have 4GB of storage, whereas the new Kindle Oasis comes with 8GB or 32GB, so storage space on older devices might be somewhat limited.