I’ve been through  a few ball heads  and always got rid of them for one reason or another, to heavy, bad handling etc.  But I think I’ve found one that is going to be in the kit for a long time,  the Acratech GV2 .
Let’s have a quick look at it. First the clamp is designed for the world standard Arca-Swiss QR clamping system, so all Arca-Swiss, RSS, Kirk, Markins, Benro etc plates will fit. Weighing in at .45kg and designed to handle 11kg the GV2 is machined from aluminium and has a black anodised finish. Suggested maximum lens is something like the 400f4 type lens. The design of the GV2 (like other Acratech products) is quite different from other brand heads, and is what I would call an open design with the tension clamp around the middle of the 35mm ball. Although it does not come apart, the design makes cleaning quite easy. I’ve only ever had to wipe or brush water and sand away as there is nowhere for a buildup of crap to hide.

The GV2 has 4 control knobs,
No1 - Main clamp knob, situated at the top the clamp knob only needs 1 ½ turn to go from fully closed to fully open so setting up, or (for those lucky enough to have two kits) changing bodies is quick. A quick note about the clamp is that it incorporates a locking indent pin which prevent a plate from sliding out if not tighten correctly, this work well with Acratech plates and some other brands, but not all so best the check before hand.

No2 – Ball lock knob, the biggest and most prominent knob which is as the name would suggest use to tighten the clamp around the ball to prevent any movement.

No3 – Tension control knob. The design of the clamping system allows you to fully release the Ball lock knob but still retain some tension on the ball, so when you release the Ball lock knob the whole thing just doesn’t fall over, it also allows you to reposition without having to keep unlocking the clamp.

No4 – Pivot Knob, situated at the base the pivot knob allows you to lock the 360deg rotation base.

The base is also engraved with degrees to let you keep track of angular movement. 
All knobs are finished in a none slip rubber coating except for the tension knob which, probably for identification when not looking, has a knurled finish with a rubber ‘o’ring around the outside.
Base of the head is fitted with standard 3/8 female thread which is the standard for most good quality tripods.

Acratech make a point of the gimble feature of this head when put into the 90deg position, all ball heads goes into a 90deg position and the only thing the GV2 has is a large diameter section of shaft where the pivot point is, properly to reduce friction and create less wear and tear at the pivot point.  Seems to work OK especially when you combine it with the tension knob function, but I haven’t compared it to anything else either.

All in all the Acratech GV2 is a great unit, it  smooth, light and well designed, and combine it with a CF tripod (I matched mine with a Velbron CF630, total weight just under 2kg) it’s hard to beat.

www.acratech.net