SportDOG Brand Sport Hunter 825X Remote Trainer - The Field Trainer 425 is the perfect system for introducing your dog to in-the-field training, or for hunting with close-working dogs. This series is loaded with technical breakthroughs in the smallest package available in this price range. Because we know that no 2 dogs are alike, we’ve designed the 'S' model to provide higher stimulation for larger or stubborn dogs.