Well they have not failed me yet but you do not want to put them together with one upside down. They are slightly trapezoidal in shape and will get jammed together. It’s not really an issue. In general I like them because they cost less and are much more compact. You don’t need a special stand to change the weights like the bow flex. I started bow flex and went to power block. I think the power lock wear worse over time cosmetically, but hold up slightly better functionally. I think they deal with drops better too.