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How to fit a martingale collar
Use a soft tape measure or piece of string to measure your dog's head.
Measure the largest part of your dog's head and the middle of their neck. If your dog's head is larger than their neck, you'll need a collar that can fit comfortably over their head.
If their neck is larger than their head, you'll need a collar that fits comfortably around their neck. Add 2 " to the largest measurement to allow for growth.