Subject : Innovative Never-Loose Self-Tightening Lock Nuts Dear Sir/Lady, We are Korean manufacturer of Innovative Never-Loose Self-Tightening Lock Nuts. Mostly, nuts and bolts get loose if they are impacted by the constant and long-lasting strong vibrations, which can drive to the mechanical breakdown and can also put the human lives to danger. Our Self-Tightening Lock Nuts are designed never to get loose from the bolts under any circumstances of vibrations of any type unless you use the tools. Please visit our web site for details. http://www.d-m-z.net/changjo/locknut.htm Best regards,Tai Whang