LEGENDplex? Carboxyl Beads are fluorescent particles designed for the multiple assay development using flow cytometers. Beads include two sizes, i.e., 5 μm and 7 μm, designated as A or B beads, and each bead set has different levels of APC fluorescence, allowing them to be clearly distinguished from each other. The functionalized carboxyl group can be used for the conjugation of antibody and streptavidin.