This Lutron® Radio Powr Savr ceiling-mount adapter bracket allows you to recess-mount an occupancy or vacancy sensor flush into the ceiling. 
Lutron® Sensor Mounting Bracket
This Lutron® Radio Powr Savr ceiling-mount adapter bracket allows you to recess-mount an occupancy or vacancy sensor flush into the ceiling. 
Mounting Details
This recess-mounting ring requires an opening of 76 mm (3 in.) in diameter. It secures inside the ceiling, while the sensor twists into the recess mounting ring so it sits flush against the ceiling surface. Note: do not recess-mount the sensor in a metal surface.