Whitehouse Scientific is a leading producer of glass microspheres for calibration and is the highest ranking European certification laboratory for primary methods of particle size analysis. The company's standards cover all particle sizing techniques including laser diffraction, Coulter methods, optical sizing, sieve calibration and image analysis. Most of these reference materials are NIST-traceable. They range in size from 0.1 micron to 5.0 millimetres and are available as single sizes or broad distribution standards. In addition, Whitehouse offers a unique calibration procedure for NIST-traceable measurement of filter apertures between 3 and 1000 microns, and also produces general purpose research grade microspheres.