Pastry Bags 101
I break down pastry bags into three catergories: paper, plastic, and reusable.
In a pinch you can make yourself a pastry bag and throw it away for easy clean up. Parchment cones (also known as cornets) are cones made from parchment paper. You can purchase a roll of parchment like I do or buy precut triangles which cost a little bit more. My favorite uses for cornets are for thin icing or melted chocolate. I occasionally use a coupler and tip with cornets, but it is not very often. Most of the time, I just cut off the tip of the cornet to produce a nice small hole for delicate decorating or drizzling.
I find myself using disposable plastic pastry bags the most. They are more convenient than cornets as they are premade and they are more affordable than reusable pastry bags up front. If you are looking to purchase some, Wilton carries disposable plastic pastry bags that are flexible enough for easy cake decorating.
There are two reusable type bags that I am familiar with: plastic coated and canvas. I recommend plastic coated over canvas because canvas is made for piping non-greasy foods and popular icing recipes use either or both butter and shortening. I do not often use my plastic coated pastry bags (also called featherweight) for cake decorating, however I do not use anything else for my Icer Tip #789, as it is durable enough to handle all the frosting and pressure.
Happy Cake Decorating!