I bought it here:
http://www2.northerntool.com/fuel-transfer-lubrication/auxiliary-fuel-tanks/item-3490014.htm
As you can see from the picture, the top/driver side is notched so that the 5th wheel hitch arm will not hit the tank (this is a short bed issue only). The downside is that you have to buy a locking fuel cap to go with it. The other RDS models don't have the exposed filler neck. You have to unlock the tool box to fill the tank.
http://www2.northerntool.com/fuel-transfer-lubrication/auxiliary-fuel-tanks/item-3490014.htm
As you can see from the picture, the top/driver side is notched so that the 5th wheel hitch arm will not hit the tank (this is a short bed issue only). The downside is that you have to buy a locking fuel cap to go with it. The other RDS models don't have the exposed filler neck. You have to unlock the tool box to fill the tank.