Synergy Overlow and return bulkhead size

[JAMSOURY]

I'm looking to get the 16" Synergy overflow and drill holes into my tank, can someone help me with what size hole I should drill for the return side? Should the size be specific to the return pump?

I have a 135g tank

Thanks!

 

[Xclusive Reef]

I have also been looking into this for a 75/90 gallon and the overflow has 1.5 " going to your sump. I am going to do 1 inch return back into the tank. I believe BRS sells the correct drill bit if you just call them and tell them you want a 1 inch return they will match you with the bit you need.