The exact values for particle size and standard deviation are determined for each lot and may be found on the certificate of analysis. These values are determined with an accuracy of 0.01 µm (Coulter Multisizer). Polymethacrylate based particles have a narrow size distribution and spherical shape. They are stable at temperatures of up to 200 °C. Density is 1.22 g/cm3. The surface is negatively charged. Good biocompatibility and reduced nonspecific protein binding are characteristic.