Many years of trouble-free use have made this one of the world's most popular pipetting aids. Accurate, precise and safe - even for use with toxic or corrosive chemicals. Simply rotate the wheel forward or backward for easy and precise filling or emptying. Color-coded by size for easy identification. When the wheel is stopped, the piston remains in the required position and holds the liquid inside until ejected. Provides a firm, positive fit for all standard pipets.