Dry polystyrene microsphere particles, also known as Dri-Cal Particle Size Standards, are very accurate in size diameter and lot-numbered for convenient technical service and support after the sale. Each Bottle includes a Certificate of Calibration and Traceability to NIST, which includes a description of the calibration method and its uncertainty; Table of chemical and physical properties; Material Safety Data Sheet. Dry Particles are sold in 1 gram volume per bottle, but can be special ordered at higher volume per bottle. Diameters of 200 μm and larger are packaged as dry Polystyrene spheres crosslinked with divinylbenzene (PSDVB).