The screws that hold the knives on the gears break, so either you know how to remove them or you go to a machine shop or open it, in the machine shop, of course, there are slots for a larger diameter screw. According to the store where I bought it, gears with a larger screw diameter are expected from the manufacturer. We'll see. However, 185 plus shipping is too much to bother with screws. If the screws didn't break, it would be excellent because it gives you the ability for exceptional control, especially around sensitive plants. February 2020. Gears with a larger screw diameter did not come, so in order to use it, I have to go to a machine shop, with the cost being uncertain. It's not worth the money in the end