As per title this RAM works on the xps17 L702x model with 2 slots. Dell will tell you they support max of 8GB (2x4), but clearly their customer service is not that knowledgeable (To their defence they shift a lot of configurations).
Also, be aware that other especially cheaper RAM may not work. I bought Komputerbay first and it did not work with this model of Dell laptop.
This is a gimmick, one that might just save your life if you are going to drive for a very long time. Personally, however I did not find this useful. I've been using shots of concentrated energy drinks for non stop drives of more than 16 hours. It is still sitting in the car somewhere (just in case), but I don't see myself using it anytime soon.