S-Fiberglass cloth, or simply S-Glass, looks and feels exactly the same as E-fiberglass cloth. However, it is made from a higher-strength glass fabric, which gives it approximately 40% higher tensile strength, and a 20% higher modulus. This fiberglass has a greater strength and abrasion resistance when used as a composite reinforcement. Additionally all of our fiberglass cloth has an aerospace grade silane finish that is compatible with polyester resin, vinylester, and epoxy resins. This finish allows the Fiberglass to have a longer shelf life and also provides a resistance to moisture. So if you are comparison shopping between E-glass and S-Glass materials, this is the superior composite material as far as tensile strength and modulus, but that strength does come with a slightly higher price.