The bands do not screw on easily. I have been canning for many decades and have not had this problem with new bands before. I managed to get them to fit on some newer canning jars, the ones that seem to have less thickness to the glass, although the diameter and thread should be the same, but the bands would not screw onto the older ones. As I said, never had a problem before using new replacement lids and bands with my "heirloom" jars. I have not tried processing yet to see if there will be a problem sealing. If I do, I will be requesting to return them. The price was a bargain, but not if they fail to perform as intended.