It does what its description says--extends the downspout to drain where you want it to drain. As far as stretching it out--I needed 4 pieces. I'm small and not unusually strong so I almost rejected this after reading reviews that said that it was very difficult to extend. The first piece did seem a bit difficult, but I did it by myself with only a little exertion and a bit of time. The other 3 pieces sat in the sun for a while before I resumed this project. They stretched out much more easily. You can start the process by flexing the piece over a railing or around your waist or over your leg. Attaching to the downspout is easy--it just slips on as does each piece onto the one before it if you are using multiples. We are expecting a good bit of rain in the next couple of days. I'll update if I find problems, but I don't expect to.
Update: No problems through rains--Everything stayed together. I'm ordering for another downspout.

Great way to redirect the rain from your downspouts! I don't know how old my previous one was since it was here when I bought my house, but it looked old and had many holes in it. This one is very thick and sturdy so it should hold up well over time. I didn't have any issues extending or bending it to go in the direction I needed it to go.

Two years later still works great. Ugly. But it works. One of my metal downspouts has continually come off, but this one has stayed in place, even through a Cat 5 hurricane. (Still baffles me, but it didn't budge.) If this were camouflaged by bushes (which I suggest), I wouldn't mind the looks. But out in plain view, it is somewhat jarring to the eye. But functionally, it can't be beat.

This is the second one I've purchased. It works well to direct water away from the foundation of my house --- but in the hot Florida sun, it was cracked and broken after a year. Still, it's reasonably priced and effective so if I need to buy a new one every year, will do so.

"Flex" is exactly what I wanted but did not get. The extension was difficult to extent to length. I had to stand on one end and give it hell with both hands to get it to move.
In order to aim it where I wanted, I had to rig guides using tent stakes, cord, and heavy rocks to keep the water diverted properly.
Final thought - It needs to be more pliable.