I’m definitely no expert but this was a very useful tool. Helped to install a complicated mortise style lock. Littler nervous how many uses I will get out of it, or where to get new bits. Durability is maybe not the best, near the end had to make sure everything was well greased and tightened so as the bit went in, the system got a bit more wobbly. By the time I finished (see photo) the bit was dual. Value to the tool though was worth it.