You just need to know what size to set them at.
I actually bought regular leg bands, thinking I would use a different color every year to track the age of my birds and it was a disaster.
Some of them slipped off birds that were smaller, adn ended up tangled in their feet. Some of them were fine when I put them on, but then the birds grew too big, and the leg bands were too tight. About 90% of the bands I put on had to be removed, some of them, unfortunately, went unnoticed until they were very difficult to remove.
We decided to never do it again. We wanted to put them on as they left the indoor pen and were put outside, so these birds were 5-6 months old, we thought it would be OK, but they still grew too big. So it can be hard. If you make them too loose, they slide up or down the leg, and can end up above the joint, or mixed in with their feet. If they are too tight, they can grow into them, or cut off circulation. I didn't like it.
Hopefully someone out there has had a better experience or has better advice than me!