Unbacked Hi-Flow™ Plus 110 and 135 membranes are offered for high protein binding in lateral flow diagnostic assays. The membranes are intended for sensitive rapid diagnostic test kits, including infectious disease, drugs of abuse, cardiac markers, and other analytes. The membranes offer capillary flow rates of 110 and 135 seconds over 4 cm to optimize immunoassay selectivity and sensitivity. In addition, these membranes have exceptional consistency and a uniform surface quality to improve reagent application.