A suspension damper includes a piston (21) that is reciprocally carried in a circular cylindrical cylinder tube (16). The piston is attached to a piston rod (25) that extends out from the cylinder tube and is adapted for connection to one of the sprung or unsprung masses of an associated vehicle. The circular cylindrical cylinder tube is carried in a reservoir tube (12) that is adapted for connection to the other of the sprung and unsprung masses. The reservoir tube includes a section with a polygonal cross section and includes an open end (15) with a circular cross section. The open end is closed by a rod guide assembly that engages the reservoir tube and the cylinder tube. The reservoir tube includes a closed end opposite the open end that is optionally polygonal or circular in configuration.
