Seeking a device like this, I asked his opinion to a physiotherapist. Do not buy junk! Use of this device requires maximum security. I can not imagine an accident with a trick that coward! So I spent a bit of time to find out and I almost immediately found my happiness here: solid, flexible and well in hand. Pulling the bungee cords range from 10 to 50 kg, ie "normal" to "super strong". To lighten the load, the elastic is unclipped (very easily) and I work for an hour with only one (dorsal muscle atrophy to treat). In short, the very reasonable price to quality. I have just a little sore arms ^^ Excellent tool that will long usage.
