You buy a flat 5 cell not a hump pack unless you plan on running it in the tail end or wire tied on someplace....don't listen to people who don't own a Jato...Jato doesn't use a hump pack like someone recommended here....they jury rigged their Jato to use a hump pack cause they didn't READ THE MANUAL...most Traxxas models don't use hump packs.....Go here or get a flat 5 cell pack...same as Revo uses.

[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHFP5&P=ML]5 Cell Battery Pack[/link]