it is not drilled, i have a single overflow. it came with the sump and a 55g tank that i purchased for $50. so i couldn't pass it up, it also came with 2 pumps and a protien skimmer. good deal huh? one pump is a rio 2500 and the other doesn't have any info on it.the one that i am not sure of the gph is the return witch will be connected to a spray bar.