We use disposable piping bags almost exclusively because they are so quick and easy to work with for piping frosting or chocolate. We use this 12 inch size most often, although larger sizes are helpful for big projects or when using jumbo piping tips (more of the bag must be snipped away to accommodate the larger sized tips).
(Amazon Description): Wilton Disposable Decorator Bags. Just use then toss. Strong flexible plastic. 12 in. size fits standard tips and couplers. Also perfect for melting Wilton candy Melt in the microwave.