The size (in milimeters) indicates the internal diameter.

2.3mm Split bird rings (SP1)

Small Finches

2.8mm Split bird rings (SP2)

Large Finches

Canaries

3.1mm Split bird rings (SP3)

Large Canaries

3.8mm Split bird rings (SP4)

Diamond and Chinese turtle Doves

Quails

4.3mm Split bird rings (SP5)

Lovebirds

Buderigar

8mm

Suitable for:

Racing homers, ducks (1 day - 6 weeks), small poultry chicks,  doves, day old pheasants.

12mm

Suitable for:

Mallard and Call ducks.

16mm

Suitable for:

Runner ducks, Bantam poultry (Pekins, Silkies)

18mm

Suitable for:

All standard breeds (Araucana, Rhode Island, Shavers) and Pheasants