It is easy to affix our fire hydrant rings to the bigger valve of the hydrant. Once the valve cap is replaced, the hydrant ring cannot be taken off until the next time the valve cap is removed. The larger interior hole, the 5.75" i.d. option, is widely preferred. It fits the 4.5" steamer- nozzles / ports. The heavy-duty plastic rings are skilfully placed underneath the hydrant’s valve to ensure that potential vandals are unable to remove the ring without completely dismantling the hydrant.