i've had the canadian magnet drain plug for a couple of years and i always get a smear of metalic paste on the end of the magnet when i change oil. it might not be the pull but the total surface space of the magnet that is best.
for 10 bucks or so i got the magnet and a hand full of crush washers.

cat

George in Easy Rider: "Oh, oh I've got a helmet! I got a beauty!"