Get the full size computer version vs the smaller labtop models. You should be happy with the strength of the mags as they almost cant be removed from the fridge unless you pry them off with leverage. They also pick up some stuff regular magnets dint even find magnetic, no not aluminum..lol Good hunting to you all!!! Oh ya test it on a vial of gold to pull off the last of the black sands and once you get the sand in the magnetic field rotate your vial round and round to scrub off any non magnetics caught up in the mag field, sometimes you can see a tiny spec of au caught in the sands, after getting any gold to drop off remove the cap slide it up and out, oh ya cover the magnet with a plastic baggie to help remove sand from mag. 
Gravelwasher 
