These filters are built on the proven design of the common "Y" strainer, but instead of a coarse screen, they contain a true micron-rated filter element whose pleated element surface area is up to four times greater. In fact, the filtering area in the "Y" filter design is equal to that found in standard hydraulic filters, but at a fraction of the cost! The flow path in the "Y" design is through the inside surface of the element, where the contaminant is caught. There can be no dirt "wash-off" of the element down-stream during servicing. This also minimizes the formation of air pockets within the filter element.