This ASO rebuild kit for the Microline Reverse Osmosis made by Clack Corporation,INCLUDES ( 1 ) of each of below:Part 2 s2005 aso capPart 3 s2013 aso cap o-ringPart 4 s2011 aso diaphragm -large ( 1 1/8" diameter )Part 5 s2007 aso pistonPart 6 s2006 aso piston ringPart 7 s2010 aso diaphragm-small ( 15/16" diameter ) - install with center "dimple" up and "flat side" down ( otherwise it won't work ).