This is a replacement Speedotron MW24Q 2400W/s Flashtube (Clear) for the 104 and 105 flash heads. Four tubes are requires per head. 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.