These are a good, high-quality velcro roller. My first set lasted a few years, and I recently purchased two replacement sets. I buy the 12-pack that comes with 3 sizes of rollers, although I believe you can buy packs of individual sizes.
I now have straight, fine, slightly frizzy hair that goes down to my middle back. I put these in immediately after blowdrying my hair, leave them in for about 5 minutes. I sometimes run the blow dryer with the rollers in, but usually not. When I take out, my hair is smooth and silky and seemingly shinier, with more body at the roots, and a slight curl at the end.
Although these are self-gripping rollers, I do use a bobby pin in each roller to hold it in place. I much prefer these to the cheaper velcro rollers. They are sturdier and hold their shape well. I think the thermal bit helps accelerate the process. And, I love how the different size rollers fit inside each other! Great for travelling.