Jerry Thirsty , Sep 17, 2006; 11:28 p.m.
I have gotten at least three "General Brand" from B&H, and they have all been Bowers brand. The thing about them is that they have a little leaf spring that, when you bayonet the lens to the camera, catches on the lens locking mechanism (this is normal, it's supposed to do this). So when you try to remove the lens, it unscrews from the adapter, rather than the adapter coming out with the lens. Then you have to use the included wrench, which disengages the leaf spring while you twist the adapter out of the body.
I have taken to just removing the leaf spring. It means that the lens won't actually lock into the body, so you have to be careful they don't separate inadvertantly, but when you do go to remove the lens, the adapter comes out with it. I've never actually had a lens come off accidentally. The closest call was with a 300/4 Takumar; I had mounted it on a tripod using the lens tripod socket and then got tangled in the camera strap or something, so pulled down on one side of the camera. It turned maybe halfway to coming free.