Heavyweight Nylon vs 2-Ply Polyester

• You're in a normal residential area (suburbs, neighborhoods, anywhere not on a coast or open plain): heavyweight nylon.
• You live on the coast, in tornado alley, or on a ridge: 2-ply polyester.
• You fly 24/7 with a light (per US Flag Code): 2-ply polyester.
• You only fly on holidays: heavyweight nylon — you'll get years of use.
• It's for a commercial flagpole over 30 ft: 2-ply polyester sized to the pole.

Nylon sheds water. The tight, low-absorbency weave means rain rolls off and the flag dries within an hour of a passing storm. It keeps flying at close to its dry weight, so the halyard, truck, and fly end aren't stressed any harder than on a normal day.

2-ply polyester absorbs water. The heavier spun-polyester construction soaks up rain and can gain a meaningful amount of weight during a soaking storm. A wet polyester flag whipping in gusty weather puts noticeably more load on the halyard and fly-end stitching than a wet nylon flag does. It's not a durability problem for the pole, but it is a reason many owners lower a polyester flag ahead of a heavy thunderstorm.

Both flags typically last 9–12 months of daily flight before the fly end starts to fray. Flag wear is dominated by the fly end whipping in wind — every gust cycle frays the trailing edge a little, and over thousands of cycles the hem gives out.

Nylon flies fully extended in lighter wind, which means more flapping cycles per day. Polyester needs more breeze to fully extend, so it sees fewer cycles — but the heavier fabric works harder on each cycle, especially when wet. The net result in a typical residential setting is a similar 9–12 month life.

• 20 ft pole: 3'×5' or 4'×6' flag
• 25 ft pole: 4'×6' or 5'×8' flag
• 30 ft pole: 5'×8' or 6'×10' flag
• 35–40 ft commercial: 6'×10' or 8'×12'