4 stars because I bought this to replace my lost left arm. I find that three hands would be most useful when assembling and I expect the same in use. A normal two-handed person might not find a fault at all. I've finally pulled myself together, but I'm exhausted to the point of exhaustion. So I need to rest before first use. The only real problem I expect is tightening the impact screws on rounded surfaces. If that gives me my left hand back, which I expect, I'm a happy camper. Having used this insurance, I believe some changes to my rating are needed. As expected, I find it impossible to properly tighten the thumbscrews to prevent parts from moving. The big loupe view is distorted and useless. In short, too many moving parts. Too bad. What could have been an easy job turned out to be a headache.