Stretch cord advice

I recently bought a set of stretch cords. When I saw the design - small plastic rings/hooks connect the bands to the interchangeable paddles and handles - I was concerned. If this was the heaviest resistance bands and I was going to be pulling on them as hard as I could (sprint training), would these little plastic rings hold up? Well, they didn't. About the fourth time I used them, the ring broke and the band snapped back to the wall in the middle of my stroke. I have seen stretch cords that don't have this design. Instead, the handles are permanently attached to the bands. And there is a nylon strap to connect the bands to a post/weight rack so one can simulate swim strokes. I've searched and searched, and can only find 'lightweight' bands for pilates with no strap to attach the cords to anything. Can anyone direct me to sturdy, heavy resistance bands that can be reliably used for rigorous dryland training? Thanks in advance!