The Arri M18 HMI Lamphead (Sliver) is an open-face, lensless, more efficient lamphead built to work with a new power class of lamp - the 1800 W SE HMI (not included), which has an average life of 750 hours, a luminous efficacy of 92 lumens/watt and a Color Rendering Index (CRI) greater than 90 at 6000 K.