The Quantum ES1 Energy Saver is the size of a AA battery, and instead of using 4 AA alkaline cells in the battery compartment of certain specific flashes, you would insert 3 AA's and the Energy Saver.
The ES1 is compatible with the Vivitar 285HV, Metz 45CL-1/3/4, 45CT-3/4, and Hasselblad 4504.
UPC: 807955009603