No.4 filters sold seperatley here.
Clever Dripper coffee brewer. 
Smart brewing device that has a valve on the bottom that releases when the device is put on top of a mug or jug.
This is the brewing device that we use in the shop for our filter coffees.
Simply 
-add a No4 filter
-rinse with hot water (and empty).
-add the ground coffee and the desired amount of hot water, 
-brew for a couple of minutes
-decant into a mug or jug (that has enough space to hold all of the liquid).