This is a set of resin 1/48 P-39 / P-400 12 Stack Exhausts from Ultracast. These exhausts replace the kit exhausts to give a higher level of detail to your model.  

Each exhaust pipe is hollow on the end.  The detail level and casting quality is flawless. 

The exhausts are a major focal point on models and these will really improve the look of this area in your next P-39 / P-400.