The RC-8 collar is compatible with all Humane Contain™ electronic fences and there is no limit to the number of collars you can have with this fence system. The RC-8 also works with the Radio Mat Electronic Scat Pad. Miniature electronics weigh only 1.2 oz. Features the proprietary Pulsed Proportional Stimulus™ System found only on Humane Contain™ brand products. High Tech Pet's advanced dog training technology is based largely upon the use of Pavlovian auditory stimulus (training tones) to reinforce the main shock stimulus. All other dog fence brands use a tone speaker that is completely enclosed in the casing to avoid failure if the speaker gets wet. This type of device doesn't make much sound and does little to aid in boundary training. The advanced RC-8 collar uses a special, waterproof speaker that transmits sound directly to the air for a much louder and more effective audible training stimulus. The training tones are pulsed to follow the shock pulse rate. This yields a powerful enhancement to the training process, resulting in quicker, easier training and a more humane experience for your dog. Add a beautiful, yet nearly indestructible, poly-elastomer strap that is integral with the electronics casing, and you've got the state-of-the-art electronic collar at an amazing value. Strap is adjustable from 7" to 25" for all dogs 10 lbs. to 200 lbs. Uses one, long-life replaceable battery (High Tech Pet model B-3V8). Shipped directly from manufacturer.