How to determine what size diameter and how much halyard you need for your flagpole: The diameter of the halyard depends on the allowable rope diameter of the pulley on the flagpole. Please confirm this diameter BEFORE purchasing.
How long should my halyard be? Typically-this is the height of the flagpole multiplied by two (2). For example: a 30' flagpole, multiply by 2 = 60' of halyard. It is better to have a little extra than not enough.
What is the difference between the nylon halyard and the polypropylene halyard? It's the chemical make up of the materials. For that reason the polypropylene can be dyed silver, bronze or black and the nylon comes in white. There is no notable difference in durability.