PB. Perko® is the original concealed door closer, offering an economic means of providing automatic closing. Solid brass round anchor plates, powder coated mechanism housing and precision-engineered chain add to its appeal.. Concealed in the door - the only parts visible are the anchor plate and the chain. Tested to withstand 500,000 open and close cycles. Fire Tested: incorporated in doors that were tested to BS476 part 22 1987. Does not affect latched 1/2 hour and 1 hour fire door integrity. Suitable for internal doors up to 50Kg/110lbs in weight in light to medium use applications