Fibers are formed from several glass compositions, the most common of which are C (Chemical), E (Electrical), E-CR (boron free E-glass) and S (strength). Continuous roving of the E-Glass type comprises the bulk of the reinforcement used in pultrusion. Continuous roving is a collection of filaments coated with a sizing that is compatibly with the resin system and brought together into a single strand called an end, or multiple strands, and then wound into a cylindrical supply package.

Bulk roving is also used in pultrusion. This product form is designed to improve the transverse properties in localized areas of pultruded composites where mat cannot be formed.