This 150 watt modeling lamp is an excellent way to upgrade the following flash heads to a brighter modeling light: -2100C Standard Head-15'Cable -2105C Standard Head-25'Cable -2110C One-Stop Switching Head -2120C Two-Stop Switching Head -2140C Three-Way Switching Head It's a professional photographer's delight that's worth the few extra dollars. The 4106 is a custom manufactured frosted quartz halogen lamp enclosed in a glass envelope. It also is an excellent,more durable,replacement to the 150 watt quartz lamp that came with some of the older style Novatron Bare Tube Heads.