I have said this so many times thus far, and I will continue to do so until my tongue falls off and I puke up thumbtacks: Wing Chun as an art is based off of structure.
Everything you will do in Wing Chun has its root- literally-in the structure of your body. From solidifying the Wing Chun yee jee kim yeung ma stance to the body unity expressed through the forms, from the reinforcement of basic concepts through the weapons of the long pole and butterfly swords to the application of Wing Chun theory and technique in a combative sense by way of chi sau and sparring training, everything boils down to one thing: structure.
A key component in training your structure is the use of the wall bag. The wall bag is to Wing Chun what the heavy bag is to a boxer. Boxers use a heavy bag to develop power, structure and rooting which forms the bedrock foundation of their entire game plan in applying their skill set. Wing Chun is no different; we need a tool to reinforce our body’s structure, rooting and power generation which will then bleed over into all aspects of training, from our forms to applying the techniques of the Wing Chun system to chi sau, weapons training and sparring. That tool is the Wing Chun wall bag.
Much care should therefore be put into choosing wall bags that most accurately and completely reinforce your structure in Wing Chun training, since the rooting and structure you develop will bleed into every area of your Wing Chun fight game, without exception.