You're installing a ceiling fan or heavy light fixture and the box flexes when you tighten the mounting hardware — or the plastic box cracks outright because it wasn't rated for the torque and vibration. A ceiling fan box has to handle both the weight and the dynamic load of a spinning fan, and most standard boxes aren't designed for it. PVC pancake box — the shallow profile fits tight ceiling cavities where a standard depth box won't work. 1-gang — single device capacity, correct for most ceiling fan and fixture installations. PVC construction — won't corrode or conduct electricity, and the non-metallic body won't interfere with the fan's electrical grounding path when properly installed. Molded mounting bosses accept standard fan-rated hardware. The pancake (shallow) profile is specifica Stocked at Crofton Lumber and Akron Lumber.