CPR bootleg.
Same concept but the acrylic is cheap & weak. Check the seals for leaks.
As long as you are careful with it...it'll be ok. Works best with an Aqualifter pump.
Of course I'd recommend drilling 1st but I have used overflows with no disasters.
There are horror stories though.
i'd second the part on disasters with hang-on overflow boxes, thank god I always bought my tanks with built in overflows. I also agree on drilling first but that might be tricky on an already estabilished tank.