Polycarbonate track-etch (PCTE) membrane filters. These filters seem to have many advantages, including precise pore sizes, low non-specific binding, and chemical resistance. They also appear to be well-suited for air monitoring, with low tare weights and superior strength. Their biologically inert properties and USP Class VI compliance make them suitable for use in medical and pharmaceutical applications. Overall, PCTE membrane filters seem like a reliable and versatile choice for a variety of filtration and separation needs.