Vaddio Ceiling Speakers are sold and packaged in pairs and optimized for easy installation and accurate voice reproduction. Ideal for conference rooms and classrooms. Key Features: 4 inch, 2-way speaker optimized for vocal clarity 8 ohm nominal impedance Ceiling or wall mountable Magnetic speaker grille and removable phoenix-style plug Included ceiling tile brace 88dB SPL 1W/1M nominal sensitivity