Was ordering a couple items from Horizon and ran across this little goodie. I can see a couple uses for it. First it could be easily set up to allow choking of a cowled in engine which is it's intended purpose. Second, with a little linkage engineering it could be used for an adjustable intake choke even on the Control Line intake. The price is sure right, I ordered a couple just to play with, think it's pretty cool.

http://www.horizonhobby.com/Products/Default.aspx?ProdId=SAI5092

Ya saw the filter.. real nice for a flight box, I like the weight and size of Master Airscrew plastic for airplanes. I seal them with a heat shrink cover.