Narrow pore size distribution for improved surface capture and analysis. Low levels of extractables to ensure sample integrity. Higher strength and flexibility Low extractable levels Narrow pore size distribution Increased temperature stability Reduced shrinkage White plain filters Cellulose nitrate membranes, circles, plain Recommended for the majority of routine applications, this membrane is manufactured under strictly controlled conditions. The user will benefit from the performance improvements that are now available in Whatman membrane filters, including very narrow pore size distribution and low levels of extractables.