This is a Dynalite UV Coated Flashtube for the discontinued 1015, 2040 and 2050 flash heads. Most current, professional flash heads and monolights are equipped with user replaceable flashtubes that may simply be plugged into, and unplugged from their sockets. With proper handling, these flashtubes may last for tens of thousands of flashes under normal use.The glass dome provides protection from contact with fingers and studio equipment.