From Manufacturer
The Acratech Long Lens Head is designed to support super-telephoto lenses as long as 600mm f/4.0. The CNC-machined Long Lens Head weighs less than 1 lb and features an Arca-style quick-release clamp that's compatible with plates from manufacturers such as Arca-Swiss, Kirk, R.R.S., and many others.
The clamp is indexable, which means it can be rotated in 90° increments by loosening the rubberized knob. This enables easy use of cameras without lenses that have lens collars, and facilitates 90° sideways tilt (rather than front-to-back tilt). While the head is specifically designed for use with extremely long telephoto lenses that are mounted with a lens collar, this feature ensures that even if you're using multiple cameras in the field, you don't need to transport other heads besides the Long Lens Head when you want to mount a camera body (with a smaller lens) directly to your tripod & head.
The tension control is fully adjustable to suit heavier and lighter loads, and the head tilts 90° in two directions. Degree markings are engraved, for precise control over panoramic adjustments. All knobs are secured so they cannot vibrate loose and fall off.