I got today the Sirui K-20X and I have a few doubts. I'm testing it with the 75-300 at both ends. First big issue is friction: I tried to find the perfect value for the big blue knob but it is always too loose (camera falls) or the movement gets sticky: nothing happens then a big jump too far. The stickiness is amplified at 300mm. I expected something super buttery, like a manual focus ring. My $50 travel velbon tripod 3-way head felt much smoother. Never used a ballhead before, neither any expensive heads. The best option is to set it even tighter, enough to keep the camera still in most positions. So with a good amount of force the movement is steady and predictable. But it is tiring to use it this way, after 2 minutes testing I can feel my arms still stiff. The panning base rotation is much smoother. There is also a little slack in the main knob movement, like 1 degree where the knob can turn back and forth without transferring any movement to the underlying mechanism. I discovered that the little friction gear does nothing but locking the minimum friction value you can use. Then the scale on the main knob is off: all loose is 5 and all tight is 2 (passing over 10), like the ring is not in the right place. No big deal. There is a very tiny adjustment movement when I leave the camera after locking the knob. Note: I'm testing it on the Velbon travel legs, fully collapsed, so some problems, like the last one, could be caused by the legs. Maybe the friction issue too, as the legs bends absorbing part of the thrust? Any suggestions?