2 1/8β bit is not 2 1/8β, it is at least 1 larger / 32 in. While this may not be important for rough work, it is very important for fine and jig work. I only bought this to replace the bi-metal hole saw I use with the Kwikset latch tool to cut metal doors. The bi-metal hole saw works, but not for as long, so I figured the carbide should last longer. But the hole saw doesn't even fit into the jig because its diameter is too big. The size of the hole a 2 1/8" hole saw leaves should be exactlyβ¦