Glass Holes Return Kit. Which one do I get?

I have a 40 Breeder that I am getting the 700 gph overflow from Glass Holes. I can't decided on what return kit to get. I want to have a duel return ( one on each corner of the tank) Overflow in middle. Should I get the 1/2" or the 3/4" return kit?



I think I will be getting the Jebao DC6000 return so keep that in mind as well.