Made in the USA! Our Underground Fence collars are designed with two heat-sealed holes, and are compatible with most underground dog fence receivers, including Invisible Fence Brand®, Pet Stop®, Pet Safe®, and Dog Guard®. Suitable for receivers with prong spacings of either 1 1/4" or 1 5/8" and a maximum prong diameter of 5/16". Please note that these collars, tailored for underground receivers, lack a D-ring and are not recommended for leash-walking purposes. UNDERGROUND FENCE COLLARS ARE MADE TO ORDER AND THEREFORE CANNOT BE RETURNED.