PetSafe Boundary Flags can be used;for any brand of underground pet fence. Boundary Flags are to be used as a visual aid for your pet to help them learn the boundary you’ve determined for them. After about 30 days, you will be able to remove the flags and your pet will know his boundaries. These PetSafe Flags are on a plastic 12 ” staff and measure 2″ x 3″. This is a bundle of 50 flags, enough to mark off up to 500 feet of wire.