Don't waste your money. Unless you buy the $50 ones they are junk. I bought the ones that have replaceable bits and broke the first one on the second hole. They do come in 5/16", 3/8", and 1/2". Usually 3/8" will do it but I also found several that had been double shot. Like N2OMike said pilot drill bits are much the same and dont break near as easily. A 3/8" hole saw will also work but not as easy to find.