WWE.com has more details on this match and its stipulation. This is what they wrote:
“Adding insult to injury, Lana then revealed that she had successfully negotiated the new terms of the previously announced match, which will see Rusev and Cena tethered at the wrist by a length of heavy-duty chain. Living up to Extreme Rules’ reputation, both Superstars will be allowed to use the chain at their discretion, whether using it as a whip or to add weight to a punch, as Rusev demonstrated on Raw.”
It will be the seventh event under the Extreme Rules chronology. This is the fourth of twelve WWE pay-per-views in 2015.