Very happy this worked to update my old ball head to an arca mount. The size of the clamp and baseplate works perfect for the bayonet mount on my ~5lb spotting scope ; may be long for smaller optics. Pleasantly surprised with the clamp weight and how sturdy it feels. The screw knob is as wide as the clamp (~2") which makes it easy to find without looking and the knurls make it easy to tension. The knob has a bubble level. The baseplate is holed and slotted such that I can't imagine you can't position it as desired.* clamp is 4 11/16" (120mm) x 1 15/16" (48mm)* 3/8" (qty 3) holes in clamp with 3/8 to 1/4 adapter included* did NOT include 3/8" stud to connect with ball head -- reused stud from old clampNormally I'm a Really Right Stuff snob but I'm hard pressed to find anything negative to say about this clamp. I'd have no problem putting my 400mm lens with a camera body on this.