IPC-4421B-AM2 an amendment includes two extensive tables of finished fabric glass styles, one in SI (metric) units and the other in U.S. (English) units. IPC-4412B standard exhaustively covers the classification and requirements for finished fabrics that are formed by plain woven glass fiber yarns. Simply, these yarns are appropriately sized bundles of continuous filament, electrical-grade ("E" glass) borosilicate glass. Bulk "E" glass, for ease of description, is composed of a blend of raw metal oxides that form a borosilicate glass upon melting. Once melted, the glass formed loses all relation to the raw metal oxides, including the network forming boron oxides or borates. Released 5/18.