Double-Acek Racing Products present the AA K21 Engine. Double-Ace Racing Products is excited to offer the AA K21 Engine to provide RC boating enthusiast with a high-performance engine with quality and craftsmanship that can't be matched by other popular RC boating engine manufacturers at a competitive price. The K21 comes with a cable collet for 3/16" cable and two head buttons. One head button is for a standard glow plug and one for a turbo plug. The engine does not come with a carburetor. A CMB 21 bolt on carb works well and Speedmaster makes a carb as well.