The 201-19 Volt has a different rear seat headrest mechanism than the 2016.  This was a minor production change that was discovered by us after it happened.  The owner's manual states that the headrests are not removable.  This is NOT true.  They are very easy to remove.  Some VoltShelf owners think the new mechanism is even easier than the old one.   As of January 1, 2017, all VoltShelf g2s and VoltMats 2s that use the headrest supports for mounting will ship with the supplemental instructions below.  These instructions are posted for owners that have received one of the above items prior to this. 

Supplemental Instructions
2017-19 Chevy Volt Rear Headrest Release
 
Due to a production change in the 2017 Volt, the rear seat headrest removal procedure has changed.  This information is NOT documented in the owner’s manual.
 
To remove the rear seat headrests:

1. Push the button at the base of one headrest post an raise the headrest to its highest position. (See owner’s manual for instructions about this, if necessary.) 
2. Locate the small hole at the base of the other headrest post.
3. While pushing the release button in step #1, use a paperclip wire or similar to poke into the hole and push lightly. The headrest should release from the seat back easily at this point.

 
If you anticipate needing to remove the headrests frequently, store the paperclip wire or similar item in a handy place.  Several options are under the trunk floor, in the rear seat armrest of console, in the front seat arm rest, or in the glove box.  Taping it in a specific location in one of these places will help you locate it more easily than if it is at the bottom of a crowded space.