This model includes both a mount to attach a fan to the backbox and a decorative covered grill to make it look less industrial. This is designed to fit the common 12v 3" marine bilge exhaust fans (exact one I used).

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Mount

Printing

• Print with 2-3 walls and 15-20% infill

BOM

• (2) M3 3x4.5x5mm heat sets
• (2) M3 10mm screws + washers
• (2) #6 x 0.75" wood screws

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Grill

• Print both pieces flat and glue together with CA or similar
• Optional M3 8mm to act as set screw for retention