Online Stores, Inc. U.S. Customs 3x5ft Superknit Polyester Flag Our printed U.S. Customs Superknit polyester 3' x 5' flag is very attractive, durable and great value. These flags are printed on a high tech silky looking knitted polyester fabric. Great for use outdoors or indoor. These flags have a very sturdy nylon header and 2 brass grommets.