I have looked at these in the past and never really understood them. It looks to me like all of them are made by 1 company and are just rebranded, there are 3 different sizes. The specifications are very confusing. It says it can filter out water and contaminants down to .005 inches with a mesh filter. How can a mesh filter filter out water? These are the key words to Google for and they come right up.
fuel filter funnel
OK i found an explanation of how they work, if they really do. It seems if there is enough water to float a boat, then it will filter some out, as long as it is not emulsified.
A mesh filter can filter out water and it depends on the mesh opening size and pressure of the liquid. The test is called a "Bubble Point" test and the Bubble Points is the pressure at which the liquid will start to pass the mesh opening.