This cowl base fits the 4 1/4 inch cowl. This part will extend the length of your cowl by 1 3/4 inch It is also used when cowl flaps are desired. There are no flap gap details molded into the part so you can cut the positions to suit your needs. The flap also hides small miss matches between the cowl and fuselage / nacelle.
Please note that the plastic we us is not Mill spec. The thickness varies + /- .002. This means that the cowl to cowl extension fit may not be perfect.
The instructions under the Parkflyer banner will explain how to improve the fit.