This marker is ideal for the size determination of PCR products. Two Ready-to-Use DNA Size Markers for Gel Electrophoresis. The 100 bp Ladder and 1 Kb Ladder represent the two most popular markers used for DNA fragment size determination. These markers are formulated to run accurately and to provide crisp band patterns. The two markers require no additonal preparation and contain bromphenol blue for ease of use. Both markers are supplied at a concentration of 50µg/500µl (0.1µg/µl).