This depends on the context it is used. Most magnetic therapy people like to present the largest number possible, so they often use the Residual Flux Density (Brmax) of the material, which really doesn't specify much about the actual magnet. This value is essentially the magnetic field density inside the magnet material. Since you will never be inside the magnet, or using the field inside the magnet, this value doesn't really have any practical value. The surface field of a magnet is a much more accurate specification for a magnet. The surface field is exactly what it sounds like. It is the magnetic field density at the surface of the magnet as measured by a Gaussmeter. This value is tested and specified for each of our stock magnets.