I have been waiting years, YEARS for this ball head.After using the RRS 55mm ball head, all I wanted was a low-profile, fast locking, eyes-free ball head from Gitzo that compromised a bit of size for ultimate stability and performance. Finally we have that in the Series 4 ball head. I went for the lever lock as it's a superior implementation compared to the competition, but this head is not without its faults. However, these faults are so minor, most people wouldn't be bothered or will find ways to overcome it.Starting with the negatives... the lever lock adjustment screw is too easy to nudge out of position. Whether they should use a screw with detents so it clicks into position, used a nylon nut to make the screw harder to turn or just recessed the head and used a hex drive so you couldn't just rub your hand across it and alter the adjustment, anything would've been better than this oversight. Having to recheck the lever lock every time you pop your camera on the head to ensure it's properly tight and won't move when locked in completely negates the advantage of using a lever lock in the first place. Worst part is you can't even loctite the bolt down because you need to adjust it for the few times you have an oddball plate that's just a tad bigger or smaller than standard.Then there's the damn rubber grips on the knobs again. These always dry out or simply tear under the torque of repeated loosening and tightening. This is especially frequent on the panning lock knob. Just use machined grooves and stop using the knob condoms.Finally, please start using an ovoid spherical ball so the camera can't just flop over when the head is loosened. All premium ball heads should have this feature and it's ridiculous it doesn't.On to the positives... it's MASSIVE. This is not for hikers and city dwellers unless you're in a studio. It's made to fit the Systematic lineup beautifully, and looks perfect on my Series 3 Systematic, but looks completely out of place on my Series 3 Mountaineer Long. The stability is excellent in the studio or out in the field, but you're going to want to hike shorter distances with this on your back or in your hand. At 2lbs, atop a 5-8lb tripod, it's substantial. However, if you're a wildlife photographer with a 600mm f/4 lens, you'll probably be happy to carry the extra weight to have the stability it brings to long telephoto lenses.The ball lock is snappy. Quarter turn and it's locked down. Reef on it if you want but it's not needed. This thing locks fast and solid.The friction pretensioner has click stops. This is excellent as you can just count the clicks if you're the type who swaps lenses or whole cameras out in the field and want to quickly set the friction. I don't know why this isn't on every Gitzo ball head.Lastly, the fluid pan feels amazing. If you do some video out in the field, you'll love this. If you're just a wildlife photographer who's scanning the horizon for your subject, even you'll love the feel of the new panning system they've incorporated. It's almost as smooth as their ball head.Even as is, this ball head is fantastic and just feels great. It's an absolute joy to use. My only hope is that they make a smaller, "Series 2" version with an approximately 40-45mm ball, and 60mm base, to fit the Mountaineer line of tripods. While I've been using mine with my Mountaineer, a slightly smaller version would create the perfect balance for that tripod. The giant, fast turning lock knob, clicky friction adjustment and silky smooth action just deserves to be slightly shrunk so all Mountaineer owners could reasonably use this fantastic ball head from Gitzo.