Well since several know, it is a valve seat resurfacing set. As you can see it is in perfect condition due to the fact that the owner had each of the tools wrapped in oily cloth when I bought it at a garage sale. The cutting surfaces are very sharp, they obviously had not been used much. To use, open the valve all the way and then unscrew the top. Take out the stem and insert the proper sized tool. Screw the top of the valve back on the valve with the cutting surface inside and the shaft sticking out of the hole. The spring which is inside provides the proper tension. Turn the tool to resurface the seat.