The relatively low price is reflected in the feeling that you should connect them carefully and slowly with the camera or lens. The contact pins make when screwing in a funny noise that I can not describe exactly. In any case, I think that this is not a problem if you always carefully touches the parts and thus protects the contacts of the camera and lens.
Despite the plastic construction, they make a strong impression. The simple locking mechanism seems as reliable and durable (perhaps precisely because it is so simple). The lenses sit so tight and jolt-free on the camera. All automatic functions of the lens are properly supported, of course, the autofocus and image stabilizer are physical limits. But you have this honestly remember that only the iris function are the real reason for automatic rings, because the image stabilization is by the inevitable use of a tripod anyway not have to be used and the autofocus does not apply to macro shots anyway most (even in expensive macro lenses) ,
Conclusion:
For an introduction to the macro photography a very inexpensive and recommended alternative. Sure, there are solid translucent but more expensive extension tubes to acquire, but I'm sure I will last a lifetime so.
As useful accessories, I recommend a macro sled. This has the advantage that you do not always have to put the tripod millimeter (very disadvantageous!) And one up to 10 cm, the camera back and forth and sideways can drive without moving the tripod. With this device you can even focus easily and thus does not have to always push down to the lens. This could in fact may in particularly short recording intervals the subject (Insect, Spider) are scared.
