Hidden door closers metal parts of the door closers are completely invisible from the surface. Compared with the conventional surface-mounted door closers, the hidden door closers are less occupying, more beautiful and concise. Lelang Hardware's RDC-04 hidden fire door closer has repeatedly opened and closed more than 1 million times. The noise of the door closing buffer is silent and the door is silent. The practicality and good quality of this door closer are popular among consumers.