A type of asteroid, fairly common in the main asteroid belt, having featureless reflectance spectra, flat to slightly reddish over the wavelength range 0.3–1.1 μ‎m. M-type asteroids are distinguished from the spectrally identical types E and P by their moderate albedos (0.10–0.18). The ‘M’ is for metallic, since they are believed to have metallic (nickel–iron) compositions. Examples of this type include (16) Psyche, diameter 253 km, and (21) Lutetia, diameter 96 km.