Used and surplus W21 beams for sale! Buy and sell W21 wide flange beams through Eiffel Trading’s online marketplace. W21 beams are a section of w-beam with a 21” dimension from flange to flange. A few popular sizes of W21 beam are W21x101, W21x122, W21x132, W21x147, W21x182, W21x248, and more. 21” w-beams are often used for temporary support structures such as falsework for bridge construction, king piles in combiwalls, beam and lagging applications, cofferdams, and much more.