RJ12 is backwards compatible with RJ11. Will fit RJ11 ports and also RJ12 ports. BE AWARE OF FAKE 'CAT6'/'CAT6a' CABLES AVAILABLE ELSEWHERE. They're a gimmick. The cable is shielded with foil and features twisted pairs for maximum signal integrity.
This product would be ideal for businesses requiring a high-quality shielded fiber optic telephone jack to support robust and secure digital phone services.
