Scroll frames are an upgrade from wood hoops. They eliminate hoop burn and the scrolling feature keeps fabric tension tight as you stitch. A frame set comes with everything you need to get stitching - side bars, scroll rods, knobs, and hook/loop tape.
The “size” of frame set refers to the length of the scroll rods. Increasing the size will increase the width of the frame for the stitching project. The vertical size of the frame can be changed by using smaller or larger side bars.
You can choose to use a Standard Tape Scroll Frame or a Webbing Scroll Frame. The difference between the two frame styles is that Webbing Frame Sets come with webbing fabric attached to the rods, while the Standard Tape Frame Sets come with "Tape for Rods" (Loop from Loop and Hook System) attached to the rods, and a small roll of Tape for Fabric (Hook from Loop and Hook System). You would stitch your fabric to the Webbing frame or use Hook Tape to attach it to the Standard Tape frame.