This is actually my design for a pan primer. Probably 30 years ago, the Buckskin Report ran a product report on it in its first design. I gave the concept to Treso several years ago and they refined the design to what it is today. It is my personal favorite of all the brass pan primer designs on the market today. It works off the same principal as a powder horn valve. It holds approximately 135 grains of Ffffg powder.
I also find it handy to use to dispense powder under the nipple of a percussion rifle, when "someone else" loads it without powder. 15.95