Review on Koopi Bi Metal Drilling Recessed Lighting Cutting Tools by James Wiley

Used this to cut some holes in my house to vent my range hood. It cut through drywall, OSB, 4 inches of Styrofoam, another layer of OSB and some siding with no problem. Just use a low speed electric drill. For the price I can't find anything better. 6.3 inch is the size you need for 6 inch vents.