Summary: I use the 391RC2 head on both my tripod and Manfrotto Car Window Mount and am thrilled with how smoothly it pivots in all directions. For my field research I have to use a window-mounted scope hundreds of times a day to read color bands of shorebirds. This head can easily swivel and then be locked in place so you can have your hands free to take notes or adjust the focus, coming loose again with another twist of the handle.
Summary: I have owned the 391rc2 head for several years and have been very pleased with not only the smooth panning, but the durability of the product. Being a hard core western hunter, I put optics and associated equipment to the test while glassing for elk and deer. Manfrotto/Bogen makes a great product, don't let the price fool you!!