How to drill my overflow?

[HarrisonMG]

Hi,
So I have a HOB pvc overflow on my 75g tank right now and it actually works well. But, its loud--too loud. Therefore I'm building V2 using a specimen container hanging on the back, with a beananimal style set of standpipes going out the bottom.
My problem is I don't know what drill bit to use to drill the 1-¼" holes in the bottom.
The manufacturer (Lee's aquatics or something) said its made out of general purpose styrene.

Any thoughts?
Thanks!

 

[mcgyvr]

Any hole saw intended for wood will work just fine.. Sometimes I run them in reverse for plastic if its biting too much...