The right side is a 12mm allen and the left is a 19mm allen.
I bought a set of 5 larger socket mounted allen bits at Advance Auto parts which included the 12 but only went up to 17. They weren't that expensive....
For the 19mm side, you can use a Craftsman (maybe others?) 5/8" sparkplug socket. You put the six-sided end in and use an extension through it to drive it...
5/8 socket 
