I got these compression devices after tearing my calf muscle. Desperate to get back to exercise quickly, and not wanting to injure my muscle further, I got these as soon as I was allowed to start training again. Once I visited the company site, it was straightforward to get the correct size (Amazon don't supply the sizing information) and they are very secure once on. They also have lasted very well through a couple of washes, and wash easily. But, for a few people (of which I am one) who have tight calf muscles, further pressure starts creating a type of compartment syndrome after exercising for some time. That means that the calf muscles start swelling, and with no place to swell to, they start compressing the blood vessels. That leads to poor blood supply to the muscle, and cramps. At worst, it can cause muscle injury although this is uncommon. I must emphasise that most people will not have tight calf muscles (I only learned that I did from my physio) but it is a warning to those people to be aware of the problem. Reluctantly, I stopped using them, and I am exercising without cramping up now.