The radio frequency-driven free-electron laser does have some particular advantages, one of these being that if you do scale to these equivalent power levels, the RF device still turns out to be smaller and lighter. Also, the RF linac is already capable of CW operation, and the light output is more suited to propagation through the atmosphere which is, of course, a primary aspect of the SDI application. We will now discuss how the basic parameters for RF linac devices are chosen, with a view toward the synergy between ion and electron linac technology.