Addition funnels are used in the lab to allow for the slow and controlled addition of a reagent solution to a reaction. The funnels provide the ability to control the temperature, speed and extent of the reactions. These funnels are typically cylindrical and are available with or without graduation marks for easier measuring. Some funnels feature a pressure equalizing arm and stoppers that disconnect from the funnel, leaving fluids isolated and unexposed. The funnels have ground outer joints, allowing them to securely fit into reaction flasks, and their protected drip stems do not extend beyond a standard taper joint. A stopcock at the base of an addition funnel allows for the transfer of a solution.