The laces seem strong but being as thick as they are, just don’t stay tied. Have to double knot them.I bought these for a rambunctious boy who breaks shoelaces constantly. I had hoped these would offer him a challenge and that they would last longer than your typical lace. They did not. They made it about (just under) a week on the first set before the outer casing ripped off, exposing the white inside. These were not as sturdy as I had hoped.