Nanosphere Size Standards are highly uniform polystyrene spheres calibrated by NIST traceable standards and packaged as aqueous suspensions in dropper-tipped bottles. 200nm /15ml. “Nanosphere Size Standards are highly uniform polystyrene spheres calibrated by NIST traceable standards and packaged as aqueous suspensions in dropper-tipped bottles. 1% solids, optimized for easy dispersal and colloidal stability. Includes Certificate of Calibration and Traceability to NIST.”