Note this is a guide only various breeds do differ in the size of their legs at different ages, so make sure you measure them correctly, the sizing needs to be a little bit bigger so it is not tight around the leg. eg: if a growing chick measures 8mm around the ankle then you would put on 11mm/12mm which gives it some room for growth without it being too big to slip off.
Lots of lines to identify??..... Use multiple colours on the leg, or use both legs, the combinations are only limited by your imagination!
PLEASE NOTE:
Leg Rings do not expand as they grow, so make sure you have other sizes available to change them into as they grow. The good news is they are reusable, so just wash and reuse, so you can change the smaller ones you have taken off and put them on some younger ones.
Measuring
This is done just above the foot, across the width of the ankle and not around it, eg: measure from the back of the ankle to the front in a straight line, (this is the widest part) do not follow the curve around the leg.