From 1950 onward, L. Ron Hubbard was intent on arranging auditing processes into a "bridge" that would serve anyone, enabling them to cross over to the "higher plateau" originally envisioned at the end of Dianetics: The Modern Science of Mental Health. A breakthrough came in the mid 1960s when LRH realized that those things which could stop auditing were the keys to unlocking higher abilities. He called those factors the "super barriers" because they were not only barriers to auditing, but the principle barriers to living. Those super barriers included communication difficulties, problems, guilt, upsets and fixed ideas.
In response, LRH reorganized the progression of auditing into bands of commonality called "Grades." The first one, Grade 0, deals with communication barriers. Over the years, many effective processes had been developed on the subject of communication; Grade 0 employs them all. Grade 0 enables a person to examine his or her personal communication barriers from all angles, and culminates not only with the willingness to freely communicate with anyone on any subject, but the ability to do so. This opens many doors to living that had previously been closed, since communication is the universal solvent.
As a rough estimate, Grade 0 usually takes somewhere around 25 hours of auditing which can generally be delivered in as little as two weeks.