Pros : Easily replaced, price is right, overall quality is good.
Cons : you can not use the center of the bit no matter what you do, UNLESS you hold the glass in your hand to use the very center of the bit. Flipping the bit over does not reach the center. The only design flaw of The Grinder and this bit system.
Other Thoughts : They need to figure out how to allow you to lower the bit so you can use the entire surface without having to hold the glass to use the very center of the bit.