A structural fiber is one that is less stretchy than the concrete it is reinforcing. This is measured by the Young's Modulus of Elasticity. To be considered structural, generally you must have a Young's ME greater than 25. There are sophisticated measures, like the ability to strain-harden, that can be considered, but the ME is a good basic parameter for separating the stiff fibers from the stretchy ones. Liwei can provide best quality PVA fiber for you!