https://wccftech.com/ps4-controller-back-button-attachment/

The PS4’s DualShock 4 controller is over six years old at this point, and yet, surprisingly, it’s still evolving. Today Sony announced the new DualShock 4 Back Button Attachment, which true to its name, gives players two extra programmable back buttons to play with. You can get a better look at the somewhat-odd new doohickey in the trailer below.

Here’s a bit more detail about the Back Button Attachment: