Just tried E-z elastic bands for for last hatch. Over thirty birds. I got the 4.5 mm which is suppose to expand to a size 7 leg band so I didn't think to keep a close eye on them. The chicks had been living in a brooder outside which I can only look down at them through. I went to move them today at four weeks to there grow out coop and found that some how only three had bands still on but all three had nasty swollen ankles and one her skin had mostly grown over the band. These do not expand at all apparently. I think they will be fine as I dug the one out and washed and bandaged them all. But I wanted to let you all know as I was hoping this would be my fix until I can fit my size 7 bands on them at ten weeks.