I purchased this GPS GSM tracker primarily for hiking with my dog in the wooded dunes of West Michigan. It surpassed my expectations. My dog will be chasing something 200 yards away, well out of sight and hearing range, and it works great. All of the stress and worry of not knowing where the dog is is gone. Because my dog doesn't stray for more than 200-300 yards, I haven't had a chance to test the full range, but within those yards and in very hilly terrain it's tracked flawlessly.