Stack hats keep out water, weather and soot. Made from high-quality polymer. Safe and easy to install and remove. Dual kit includes two stack hats and an extension pole. No moving parts. Fits 5" stacks. 12-1/2"L. One hat is 5-1/2" dia., the other is 5-3/4" diameter. Hats stack inside one another for more compact storage. 
Sold as a dual stack kit. Available in red, blue or black. 

Does not fit Peterbilt and Freightliner OEM curved top stacks. Will fit aftermarket curved top stacks.