Wobble-not serological pipets have a patented innovative 2-tier step design at the plug end vs. traditional pipets that have a straight cylindrical-shaped plug end, requiring less insertion force Wobble-nots are the only serological pipets that will give you two zones of contact in your pipet controller's nozzle, to increase stability and reduce dripping Ultra-clear markings and color-coded stripes for quick volume identification 25 & 50mL pipets feature negative graduations to -10mL Premium polymer fiber barrier plug Accuracy ± 2% at full volume