The Bf 109K was made up of the best features from the many versions of the 109G. The 109K was powered by the DB 605D engine, with the possibility to have either MW powerboosting or extra standard fuel. The engine mounted gun was changed to the Mk 108 cannon, used in some later versions of the 109G. The 12mm MG 131s were retained as the cowling guns. The resulting fighter was roughly twenty miles per hour faster than the Bf 109G-10 at all heights. K-4 was the main K variant, first appearing in October 1944, and at least 544 K-4s had been produced by the end of November. Shortages of both the engine and new gun meant that the older 109G remained in production at the same time as the K-4. The exact total of K-4s that were built is unknown. Plans were in place to build over 3,500 by July 1945, but work didn't begin at all of the factories involved.