Shodashakshari Mantra: This is one of the famous and powerful mantra, and its secrets are unexplainable it has 16 letters.
This mantra is –
Ka Ye E La Hrim Ha Sa Ka Ha La Hrim Sa Ka La Hrim Shrim
Panchadashakshari Mantra: This also very powerful mantra, and it has 15 letters; and it is also called Shri Vidya Mantra.
It is –
Ka Ye E La Hrim Ha Sa Ka Ha La Hrim Sa Ka La Hrim
Note: The difference between Shodashakshari & Panchadashakshari, Mantra is of Shrim only. These mantras are the most powerful, miraculous, mysterious and unexplainable. Only a fortunate disciple gets diksha of these mantras from a Guru, and these mantras starts opening the secrets of the life and beyond the life.
These mantras are tested and have been used by number Gurus and Masters of India. A mantra actually becomes a mantra when it is given the by the Guru, and a Guru tells a proper guideline and procedure.