FA170-6 Square Grill for 6" Strategy Speakers by Atlas Sound is acoustically matched and treated backboxes allow Strategy Series loudspeakers to perform with optimum resonance-free operation. Each units include three, easy-toadjust clamps that rotate and secure with a screwdriver into ceilings up to 11/4" thick. This unit is undercoated and equipped with four threaded loudspeaker inserts and three grille-stud receptacles.