Due to space the Fi unit takes up, it is not as adjustable as other collars. The larger the collar size, the more adjustable it becomes. The smaller sizes are less adjustable.

A 12” collar should be adjustable about 11-13”.

When adding a custom ID to collar sizes 12" to 15", we recommend a maximum of 14 characters per line to ensure that ID information is not covered up by the adjustment hardware.

Here are some sample sizes:

13” adjusts ~ 12-14” | 14" adjusts ~ 13-15" | 15" adjusts ~ 14-16" | 16" adjusts ~ 15-18" | 17" adjusts ~ 16-18" | 18" adjusts ~ 17-20" | 19" adjusts ~ 18-21" | 20" adjusts ~ 18-23" |