With design-related defects

After my very positive experience with the plastic clamp for the 100 mm L 2.8 macro from the same manufacturer (JJC), I decided to purchase these clamp. I had the (false) idea to get one up on diameter and color equal engineered product. This is not so! The clamping of the clamp is performed completely differently. Here not about pulling the bolt, the two ring halves together as in the macro lens, but the screw exerts here with their head pressure in a way inclined plane of the counter ring, whereby the clamping force is to come. But of course, plastic is not hard enough, the principle itself is ill-conceived and even from the pure physics ago hardly possible. Screws are nunmal konstuiert for tensile loads and not for selectively build high pressures.
In practice, one does not make it then, to get the tripod clamp securely. The screw grinds and groans questionable and if it is so strong that they can no longer continue to rise with the hand, the clamp can still turn on the lens. That's useless crap. The existing clamping force thereby spread obviously not on the entire circumference of the two ring halves (as just the macro) but acts mainly at points where just pushes the screw tip in the material. In my view, therefore, a bad design. I do not recommend buying therefore