Accessories and Documentation
In a zip lock bag found behind the mouse, there is a second rubber insert to use with the Rival. If the "RIVAL" one does not do it for you, maybe the one with "SteelSeries" and the logo will. Thing is, anyone with a 3D printer could make any sort of insert they wanted, and it is a very cool idea.
As for paperwork, this is it, just this two sided piece of paper. This side covers help and safety. It offers the support, FAQ, and explains where to shop with SteelSeries addresses. The bottom discusses ergonomics a bit, then mentions that breaks are definitely needed while gaming.
The reverse of that insert offers a quick tutorial. First plug in the Rival, then get online and grab the software. Funny thing, the software. While this and the box show various charts and graphs for the software, the SteelSeries Engine 3.0 shows something completely different.