These filters is required when connecting a phone to a phone jack that has DSL. It filters the DSL to allow high quality voice communication using the standard touch tone phone. Not using this filter can result in poor voice communication, but more importantly, will reduce the data speed of your DSL!
Can be used for Computers, Fax Machines, Printers, Home Phone Systems, and other devices compatible with phone cords.
Condition is New, Open Box. Notice that one is missing from original package so it is a pack of 4 not 5.
Shipped with USPS First Class.