25 Pack - Low cost ADSL Filter, used with any ADSL Router / Modem for connection to socket's throughout the house. To ensure conneciton you will require one of these on EVERY extension socket within the house.Compatibility: Any standard broadband router/modem connected to a BT line, eg BT Openworld, BT Business, Tiscali, AOL, etc.. (Note these units are not required for cable/telewest/NTL type routers) Simple design, easy installationConnectivity: Phone & ADSL Router/Modem1 x RJ-11 socket for DSL Connection 1 x BT431A filtered socket for Phone/Fax connection. 2 year Ex-Pro Warranty.