16v Rear Brake Help

[davidwinchell2 at sprynet.com (David L. Winchell, II)]

I finally got some time to work on this car this weekend.  I bought new
front and rear pads (cheapies until I can upgrade the rotor and pads front
and rear with braided lines.) I got the front calipers loose when I realized
they gave me the wrong pads for the front.  I took them back to the store
and of course the correct pads have to be shipped. So, I come back home get
the rear caliper loose and find that the hex tool required to mover the
piston back into the caliper is much bigger than even the fattest one I
have.  My question is what size hex tool (allen wrench) do I need? TIA

David L. Winchell, II
DavidWinchell2@sprynet.com
87 16V Scirocco
86 8V Scirocco
01 V6 Galant
00 Silverado
www.cardomain.com/id/xavsbud