You won’t need stop collars like these on most drill presses, which come with built-in stop systems, but they are very handy for handheld drilling, where the alternative is a tape flag that mangles easily, allowing you to drill too deep.  

As opposed to standard stop collars, which fit only one bit size, these innovative collars are engineered to fit a range of bits (1/8 to 1/4 in. and 1/4 to 1/2 in.). They clamp squarely and firmly onto every bit in their range, thanks to smoothly curved interiors that register just as well on the fluted part of the bit as they do on the smooth shank. And their lower edges didn’t mar the wood in my tests.  

For just $35 you get a pair of stops that will fit all bits between 1/8 in. and 1/2 in. dia. That seems like a bargain to me.