This is an Arri Compact 4000 HMI Fresnel Kit. It includes an electronic ballast, 50' cable, filter frame and barndoor set. The ballast is dimmable via a rocker switch, or your DMX control board. Where compact, lightweight Daylight Fresnel spotlights with high efficiency are required, Arri is the preferred choice.
Arri's elegant modular construction, using corrosion free aluminium extrusions and light weight die castings, offers great structural strength and weather resistance. Together with the Arri flicker-free Electronic Ballast, the rugged Compact range is the ideal choice for all locations. An HMI bulb is required, but not included.
 
Source from B&H Photovideo.com
https://www.bhphotovideo.com/c/product/72219-REG/Arri_Compact_HMI_4000_Watt.html