The cap is made of plastic, but makes a robust impression. Only the Focus lever is, as described by others, very lapperig and can be adjusted slightly. The snap points are very very soft and that's the only reason a star is missing here.
For that I am pleasantly surprised at how the pictures look, whose light has been squeezed through this lens. The fixed aperture of 8.0 is here responsible for ensuring that much is as sharp as possible, the Hyperfocaldistanz is according to my calculations at about 70cm. In fine weather, so to capture wonderful images with good sharpness when it's dark you need just a tripod or flash.
When Focus one has to rely a little bit on experimentation and trial and error. Most recommend that "infinity" to avoid setting and to use the funds for setting landscapes. For me, the pictures are just "infinity" with consistently sharp *, with the center position distant elements are with me blurred or washed out. The 20cm-setting, you can record close subjects, incidentally, can thus make funny Selfies. Simply keep the face in front the lens and pull the trigger. May look while creating the Selfies pretty crazy, the result is convincing.
Overall, the lens is a lot of fun, I'd buy it immediately and no longer give my forth.
If someone plays with the idea to add itself a fisheye, and not sure whether you can take the effect cope with this cap you have the opportunity for a little to see the world through the eyes of a fish :-)
But one thing must be clear, this is not a professional lens. However, I am of the opinion that this cap is more than just a "fun lens".