In the mid-1970s larger scales were introduced, including detailed -scale models of the Spitfire, Messerschmitt Bf 109, Hawker Hurricane and Harrier "jump-jet". The mid-1970s were a peak time for Airfix. Releasing as many as 17 new kits a year, Airfix commanded 75% of the UK market with 20 million kits per annum. Series 20 was limited for several years to the 1972 scale kit of the 1930 Supercharged Bentley 4.5 Litre car, with 272 parts and the option of a 3-volt motor. In 1979 four motorcycles in scale were added to this series. The company also introduced an addition to the very popular plastic soldier boxed set line with a scale version.