No problem - if you want to filter metal, the north-pole of the magnet should show to the right side of the motor.
If you want to filter nylon, you only have to turn the north-pole to the front of the bike.
Seriously: if you've ever seen a magnet like this after one season of use, you will definitely not want to do without it in the future.
Even a fit bike that goes well, has metallic abrasion. Just look at the pitting on a well-used gearbox.
If the metal residues are "caught" on the magnet, they no longer cause any wear.
Thomas aus LAU