DiagPoly™ Plain Fluorescent Polystyrene Particles, Red, 500 nm are monodispersed fluorescent polystyrene beads(PDI < 0.08, likely around 0.03) using rhodamine B (CAS # 81-88-9, Ex/Em=552/582 nm). Ex/Em=552/578 nm. Supplied 1ml at 1% solid dispersed in 0.1% Tween 20 in DI water containing 2mM NaN3.