These long link chain collars are supplied in the UK by company who have been manufacturing chains since 1870.
Sizes available are as follows:
51cm /20" width 4mm
56cm/22", width 4mm
61cm/24", width 4mm
66cm/26", width 4mm
To determine the correct size, measure your dog's neck and add 2" to 3". Double-check by measuring round the widest part of the dog's head to make sure the chosen length will fit over his head (allow about 2" for the end rings for a 3mm chain, a little more for a 4mm chain).