We have been using these chains at work for a while now and it seems like lately whether they got a bad run of them or what I have no idea but we have been breaking at least one chain every 2-3 weeks. It's not from sharpening. We have had brand new chains break within a couple hours of use. We have had ones with teeth that are tweaked to the sides. They must be cheaply made with as fast as we go through them. We dug through the truck one day and had six or better that had busted. I can see if they'd been sharpened wrong by the new guy or something like that but we've put them on with new bars and still snap.