Shoemaker 100-16X16 16"x16" Step Down Ceiling Diffuser - White 100 - Diffuser Only (No Damper) 100 D - Diffuser With Steel Multi-Shutter Damper 100 O - Diffuser With Steel Lever Operated Opposed Blade Damper Countersunk Mounting Holes For Flush Appearance With Color Matching Phillips Posi-Drive Screws