If you have ever loaded a shell and forgot to put a primer in you will know the pain of shot and powder going everywhere.
The powder/shot catch will catch any powder or shot that falls through your shell.
The powder and shot catch fits under station 3 on you MEC 600 there are 2 variations one to fit the pre "82" MEC's and on to fit the 600 mk5 version. The pre 82 version fits into the recess in your machine, the mk 5 version fits under station 3 on your machine, both powder catchers have embedded magnets to hold them in place when in use.
