A new head locating screw (#24566) with nylon filter has been introduced to prevent contaminants from reaching the advance piston area. See Figure 4-66. The filter is installed into the body of the screw, the end of which is crimped over. The screw is only available as an assembly, as shown on the right, and is identified by a groove around the head of the screw. Suitable for use in all mechanical light load advance-type pumps.