This thingy is a snap-on adapter for Xbox One controller, meant for people with disabilities - without fingers or without full control or one hand. 
Playing with WASD in such situations is not easy. Gamepad's joystick is much more convenient, however, some games still require using LB/LT buttons. Applying this snap-on allows controlling those without any weird gymnastics - Try playing e.g. Detroit: Become Human quick-time events with one hand to know the pain...

Extension moves bumper and trigger buttons to another side, so the user can easily operate all 4 front buttons with one hand. 
Once assembled, this add-on can be attached/detached in seconds and doesn't require any tools or gamepad modifications. It also does not cover any port on the gamepad.

Well, I wanted to design this kind of device for myself some time ago, but it wasn't on my list of priorities until recently :)
Snap-On Controller Mods contest on Prusa website was a great opportunity to finally start working on this project.
This is gaming equipment, so the primary objective was to make it look good, doing its job properly in this case is a side effect. So far, it works really well :)