These bits are incredibly bad. I used them Yesterday one of the middle bits broke on hole 6. Then I went up a size and it broke on hole 1! If you don't drill holes in styrofoam, find something else. You will have more fun burning a 10 dollar bill.
Pros
Quick Change: 1/4" hex shank fits all 1/4" hex shank drill bits easily and securely and is designed to hold in the quick change chuck