QSC Audio AD-C81TW Ceiling Mount Subwoofer System (White) - Manual (Page 7)

AD-C81Tw Dimensions
CUTOUT HOLE DIAMETER = 297 mm (11.69) USE C-RING FOR TEMPLATE
MATERIAL THICKNESS RANGE FOR CLAMP MOUNTING = 5.6 - 19.0 mm (0.22" - 0.75")