When selecting fiberglass (FRP) fence posts, prioritize UV resistance and tensile strength. Ensure the posts are manufactured using the pultrusion process, which provides superior longitudinal strength compared to molded alternatives. For agricultural use, a diameter of 8mm to 12mm is standard, while industrial security fencing may require square or rectangular profiles with wall thicknesses of at least 3mm. Always verify that the resin content includes UV inhibitors to prevent 'fiber blooming' (surface degradation) under intense sunlight.