With the incorporated stopcock, the dropping funnels or addition funnels manage the slow content transfer. Stoppers isolate and protect critical fluids by disconnecting the funnel and pressure-equalizing the arm. The laboratory glassware is typically cylindrical and comes with or without calibrated graduations for visible measuring during reagent addition. The ground outside joints allow the vessel to fit snugly into the reaction flask, and the protected drip stems will not extend beyond the usual taper joint. A glass tube connects the ground glass joint from the bulb of the funnel to the ground glass joint on pressure-equalizing versions. Dropping funnels come in a variety of capacities.