Few tips to make sure that this works right: Pulling the sleeve hard after it has been wound up is the most important part. It should unwind so fast it sounds like a humming bird. Rather than using a sleeve, some people have had success with the leg from a pair of tights. That may even be easier.
You can hold the eggs up to a flashlight before boiling to check if they have been properly scrambled. A scrambled egg will let no light through or at most a very small amount of red light, a normal egg will be much brighter and have a yellow tint.
Be sure that the strings or rubber bands are tightly on the sleeve or the egg will be out of balance and be impossible to spin fast enough for it to work properly. Also, the eggs are weakened by doing this and sometimes tend to pop if cooked in water at a full boil.
To cook properly, place in water on the stove and heat until it’s hot enough that bubbles start forming on the shells, but not at a full boil, then turn off the burner and let the eggs sit in the pot for 15 minutes. When the time’s up dump the eggs in cold water to cool them quickly so they don’t overcook.