Yup. The bit will cut right around the circle like a saw. You don't end up with a perfect circle like you would with a barrel bit, but unless you have a drill press the barrel bits are very risky to use. On really thick glass the dremel takes some work, but on a smaller tank it's nothing. It takes me about 10 minutes per hole with a dremel. Once the initial hole is drilled you can just go to work. There is little to no chance of breaking the glass after the hole is drilled.