I disagree, I have a few dozen of them (Idont want to wash them every week, and I run 3 at a time) I have to run them through the washing machine 2 times using bleach the 1st. They are impossible to clean by hand, they trap particles down to 100 microns. If you are planning to run 1 sock I'd buy atleast 6 of them this way when you wash them you arent wasting a load of water to wash 1 sock, they are fine if they dry out while waiting for enough to do a load in the wash machine.