How to mount LEE Numeric Edition filters on Canon's 420EX and 550EX. Knowing of the often-sold Lee 204 for "Party photography", I decided I wanted one as well --- and a lot of other filters. I found that the Lee Numeric Edition is very cheap to acquire for the numbers of filters included, and they are just large enough for my mobile flash heads. This graphical HowTo and the images and texts it consists of are available under a choice of free licenses, so use it, share it, enjoy it!