[2015 Upgrade Underground Dog Fence] Esky In-ground Electric Pet Fencing System with 2 Shock Collars, Over 1.2 Acres Range, Fits 30-100LBS Dogs Fits dogs: Weighing 30-100LBS, with neck sizes of 1-18 INCHES Designed for two dogs inside the same fence system Up to 5000 square meters range(over 1.2 acres) No limit to the number of collars it can control. You can add two or more collars into the system