Conceptually this is an excellent idea, but in practice, it gives mixed results. The provided collars fit most common drill bit sizes. While the collar fits snugly on smaller bits, on larger ones (>8mm), it's difficult to tighten the grub screw in many positions of the bit since screw can easily slip into the flutes and the collar comes loose. And when you do manage to find a good position, the collar sits at an angle. But with a little maneuvering you can find a position that works. Aside from this minor drawback, it's a handy little thing to help you drill holes at consistent depths.