Annarie the leg band you ordered the snap bands from foy's, been using those for a few years
the small ones are good for chicks, med for larger chicks, the 10-18 mm ones for adult birds, i keep a box of 3 colors each of all the sizes (4 for the sm and med) and a sharpie to mark a number on them if needed. going on 3 years for my free range hens wearing them. the only time I have a problem with them falling off is if they are not snapped right, no problem with them getting brittle
the small ones are good for chicks, med for larger chicks, the 10-18 mm ones for adult birds, i keep a box of 3 colors each of all the sizes (4 for the sm and med) and a sharpie to mark a number on them if needed. going on 3 years for my free range hens wearing them. the only time I have a problem with them falling off is if they are not snapped right, no problem with them getting brittle