Buying a pet identification tag for your Cairn Terrier is like purchasing an insurance policy – you do so with the devout wish that you won’t use it. The “possible cost” of not having a pet ID tag is more costly than the “actual price” of purchasing the pet tag itself.
The type of pet ID tag that you buy is crucial, so take five minutes or so to consider it. Whimsically picking a collar tag just because it’s low cost or trendy usually ends up being unwise, long-term.