These filters are best suited to high volume sediment removal situations where size and space limitations demand the use of smaller housings, e.g. boats, caravans and some house supply situations. Pleated pre filters catch all particles down to their rated pore size on the outside surface. The pleating increases the surface area significantly and hence the effectiveness of the pre filter. This style can be hosed clean in most situations and can be used a couple of times. The American Harmsco filter below is more expensive but has 50% more filter area.