Filter support assembly for collecting dust particles in a stack sampling system. Available in either 51mm (2"), 76mm (3") or 102mm (4") (illustrated) size. Consists of: PART A, with 28/15 outer joint bent perpendicular to flow path; PART B, with seat for fritted disc and 28/15 inner joint; PART C, neoprene gasket used to seal filter paper and prevent leakage around filter; PART D, porosity B fritted disc. Use 7670-18 to clamp 51mm size, 6509-03 for 76mm size, and 6509-05 for the 102mm size.