Protein molecular weight markers, sometimes identified as protein standards or protein ladders, are used to estimate the molecular weight of proteins of interest, to monitor the progress of electrophoretic separation or transfer, and as a positive control for analysis conditions. The marker provides a set of references optimized for consistent migration that can easily be compared to experimental gel run results. Prestained markers allow easy tracking of separation and transfer. Unstained markers provide more precise determination of molecular weight. We offer a wide selection of markers for numerous protein electrophoresis applications, including silver staining, isoelectric focusing, fluorescent studies, Western blotting, and many more. All have been use-tested to assure outstanding performance and are available in convenient package sizes.