The Ceramic Metal Halide bulb (CMH) or Light Emitting Ceramic (LEC) are two different terms that both refer to the same technology.
A CMH grow light is like a Metal Halide (MH) bulb. However, while a MH bulb uses a standard quartz arc tube, the CMH is built with a ceramic arc tube. This is similar to the material used for HPS grow lights. Therefore, CMH is a mix of MH and HPS.
Since it uses ceramic arc material, CMH is less degradative than both MH and HPS with up to 20,000 hours of lifespan. CMHs can operate at a higher pressure and emit stronger light output rather than HIDs as well.