The 4L4 fusial thrust engine represents an engine manufactured by the Incom Corporation specifically to power their T-65B X-wing starfighters. Each T-65B X-wing was equipped with a quartet of 4L4 fusial thrust engines, with one engine situated on each individual wing. A 4j.4 fusial thrust engine was designed to be a compatible alternative, capable of substituting for the 4L4 fusial thrust engine.