Select the outer most circle of faces and extrude them out straight out using the scale in global mode. To get into global mode, click on the small circle on the top right of your extrusion manipulator. Then Scale on the X axis.
Select again the faces you just extruded and extrude them again, this time stay in local extrusion mode, select the scale on the X axis and then scale them in.
After you have them the size you want extrude again. Scale those out on the X axis globally.
