What size drill bit for 1/2" ebb and flow fitting?

I am getting everything I need together for a little system but I am unsure of what size spade drill bit or hole saw to use for the 1/2" ebb and flow fitting. This is the 1/2" fitting that I plan on ordering http://www.plantlightinghydroponics.com/12-ebb-flow-tub-outlet-fitting-p-1652.html

Thanks guys!

I believe it's a 1-3/8" bit.. good lucc!

i use a 13/16in spade bit for installing 1/2in grommets in buckets..good luck. peace

I just called my local hydro shop and they said it's a 1 1/4 inch spade bit.