I bought these bits to make t-slots on my table saw and other tools myself. I used a 1/4" bit after first cutting a 1/4" wide slot and then using a 1/4" bit to cut the wings. When I tried just the bit to use to cut both parts of the T-slot, the piecework wandered. The slot fits the head of a 1/4 x 20 hex screw, or you can set the router to make a slot for T-screws (eg. B. toilet seat screws). The bits appear to be reasonably sharp and well made.