Medium Density Fiberboard

Plywood Laminated veneer lumber Particle board Medium density fiberboard High density fiberboard

The 2008 National Electrical Code (NFPA 70) Article 410.136 (B) requires surface mounted luminaires containing a ballast to be listed for mounting on the fiberboard or they must be mounted not less that 1 1/2 inches from the surface of the fiberboard.

Medium Density fiber board is 48 lb. board. High Density Fiberboard is 55 lb. board. Low Density Fiberboard is 38 lb. board. Ultra Light Fiberboard is 33 lb. board.

Well one of them is kind of dense while the other one is not really dense at all.