A. Some disposal manufacturers recommend using the rubber gasket that comes with the disposer. However, other disposer manufacturers recommend using plumbers putty. We believe if the flange is properly installed using plumbers putty, the installation will provide a seal for a longer length of time than the rubber gasket. When a flange is installed with plumbers putty the putty will keep water from leaking through it. The plumbers putty will also stay pliable over time. As the sink is used water comes in contact with the plumbers putty which slowly absorbs into the putty. The water actually acts as a lubrication for the putty and helps keep it from drying out. This is why sink flanges installed with plumbers putty can function for 20 years or more without leaking. If the sink is not used for 4 months or longer the putty will begin drying out which will lead to leakage when the sink is again used. If you have more confidence in using the rubber gasket and can live with small amounts of water left in your sink, then by all means use the rubber gasket.