Composite fabrication has many processes. Some of the most important of these processes are hand and automated tape lay-up, resin injection, compression molding, pultrusion, and filament winding. The most commonly used processes can be divided into two categories: high- and low-volume. Advanced composites are typically used as laminates. In the filament-winding process, roving (a form of glass fibers made of filaments or strands gathered together to form a bundle) or tape is drawn through a resin bath and wound onto a rotating mandrel. Pultrusion consists of transporting continuous fiber bundles through a resin matrix bath and then pulling them through a heated die. Filling a niche between hand manufacturing lay-up or spray-up of parts and compression molding in matched metal molds is resin transfer molding (RTM).