This product is either discontinued or we cannot get that from suppliers.
Ubiquiti Ceiling Mount FLEXHD-CM, Magnetic 3 1/3” inch (85 mm) face plate, Requires 2 1/8” inch (54 mm) cutout, Adjustable, sliding retainer for mounting without screws, Includes drywall mounting hardware and anchors.
The Ubiquiti FlexHD-CM-3 is a recessed ceiling mount accessory for the UniFi FLEX HD access point. Mount the UAP-FlexHD to a drop ceiling tile, drywall ceiling or solid ceiling for discreet, low profile appearance.