What type of pipets are graduated from a zero mark near the top to the tip?

Serological pipets are specifically designed with a graduation that extends from a zero mark located near the top down to the tip. This design facilitates the measurement and transfer of specific volumes of liquid, allowing for accurate dispensing based on the graduation marks. The wider graduation scale allows for a range of measurements, making them versatile for various laboratory tasks, particularly in the preparation of solutions or samples.

In contrast, volumetric pipets are calibrated to deliver precise volumes of liquid but do not have graduation marks down to the tip; they typically have a single mark that indicates the exact volume they are designed to deliver. Micropipets, while also used for measuring liquid, operate differently by using a push-button piston mechanism rather than the calibrated graduation method of serological pipets. Filter pipets, on the other hand, are designed primarily for removing particulates from liquid rather than measuring volumes and do not have graduation marks for accurate volume measurement.