Abstract: A small, high performance quadrupole mass analyzer (QMA) that is simple to manufacture and assemble with high precision due to the design of key components using high precision circular geometries that are easily machined. The QMA has a single, cylindrical insulating retainer block, which supports at the four filter rods at their mid-points and precisely positions them in the conventional quadrupole configuration. The rods are held in the retainer block by radial fasteners that extend in radially from the outer diameter of the retainer block. These fasteners also constitute the electrical connection for each rod. The retainer block has precise outer diameter for alignment with the entrance and exit electrodes, each of which has a lip of matching precise inner diameter that fits over the outer diameter of the retainer block, thereby achieving virtually perfect coaxial alignment of these parts with one another.