How to select replacement flagpole rope
A flagpole halyard must fit the pole's pulley, routing and attachment hardware. Before ordering, check the flagpole manufacturer's recommendations and the existing halyard's size and construction.
Diameter and length are separate decisions
A rope that is too thick may not pass freely through the pulley. A rope that is too thin may not work well with the installed cleat or other hardware. Measure or identify the original specification before replacing it.
Determine length from the complete route the rope follows, including both runs where applicable and the allowance needed at the cleat and attachment points. Pole height alone may not describe an internal-halyard system.
Compare construction
Polyester and wire-core halyards are different configurations. Confirm whether your pole requires a core, particular splice or other termination. Do not assume that a core makes a rope unbreakable or tamper-proof.
Installation and inspection
Inspect accessible hardware for wear and arrange appropriate professional access for work at height. Check the replacement after installation and inspect it periodically according to the pole and rope manufacturer's guidance.
For your next suitable craft or utility project, browse currently available Ravenox products and compare rope diameters and lengths. Check the selected option's intended use and availability before ordering.

Comment
I need rope for a 50-60 ft flagpole.