Can anyone please tell me HOW to use the Little Genie Magic Bobbin Inserts? They are supposed to be inserted in the bobbin case to make the bobbin run smoother and help prevent bird's nests.

MY PROBLEM: HOW & WHAT DIRECTION is it supposed to be put in the bobbin case??
The directions just say to put it in>>.........
THE PROBLEM: WHICH/WHAT DIRECTION??????
They are NOT flat--They are concave on one side and convex on the other////////////
I cannot figure out which way to put them in the bobbin case---thus way or that way????????
I've had tension and bobbin case issues and am concerned about messing stuff up if I put them in the wrong way,,,,,,,this is AFTER 3 DIFFERENT repairpersons, 3 "THIS is the RIGHT/CORRECT BOBBIN CASE"s, and 3 needle/throat plates...--
ANY IDEAS/HELP WILL BE APPRECIATED..