The Elva 300 was the last Formula Junior model produced by Elva and it was the lowest FJ of its time measuring a mere 24-inches high. Since the company was nearing bankruptcy, the car was never fully developed and was considerably slower than the competition. In total, only six examples were created.

One of the flaws were its drum brakes which did not offer the same performance as many other disc brake cars of the time. The first car, chassis 001, had a very short life, though it did carry Mark Donohue in his single-seater racing debut at Nassau Speed week. There were two chassis number 003 - one was sent to the US for Chuck Dietrich and the other was a works car driven by Chris Ashmore. Ashmore's car was powered by a Cosworth engine which was underpowered against many other FJ racers of the time. The car passed through several owners, eventually making its way to the United States. As the years passed, modifications were made to make it quicker, which eventually happened. Disc brakes, different engines, suspension modifications, and several other tricks were tried.

Currently, there are four Elva 300 cars still in existence. The cars had a tubular spaceframe chassis, fiberglass body, Elva magnesium wheels, drum brakes, and rack-and-pinion steering. A Volkswagen four-speed gearbox and a double-wishbone suspension setup was common.