If the Rallye 4000 is the standard to which all other lamps are compared, then the Rallye 4000FF is the next evolution of reflector technology.   So much so tha this lamp outperforms the Standard Rallye 4000 by over 40% with a 55W bulb.   The Standard Rallye 4000's come with a 100W bulb.   So, you get better performance with less electrical draw on your system.   The 4000FF's kepp that was good about the 4000 series and inproves on the output.  

The mounting base measures about 3 1/4 inches wide and "cradles" the shell in a 7" cup of metal for the most stable mounting systems available in the industry today.   Two knurled knobs perform the adjustment and position-locking function.   Loosen these knobs and you can rotate the shell up, down and side-to-side for a full range of adjustment.    Tighten them and the shell is snugged into a rubber gasket between the shell and the mounting cup.   This will hold the lamps in the position you want perfectly!