These are Master sockets but can also be used as Extension sockets by snipping out the Yellow Capacitor inside.
3 x genuine BT 2/1a Telephone Socket Extension Master Socket BT Line Jack Unit
10x 4/2a Twin Telephone Socket Flush (PABX Master) BT Line Jack IDC Terminals
10x 4/1a Twin Telephone Socket Flush (Full Master) BT Line Jack IDC Terminals
2/3a Telephone Socket Extension + Back Box + (Slave/Secondary) BT Line Jack Unit
2/1a Telephone Socket Extension + Back Box + (Master Socket) BT Line Jack Unit
