...... For 21 mm internal diameter as indicated they do not fit. Even for the 19 mm expansion mechanism was too small. I have a piece of PVC tubing over it pushed, now it fits. Therefore, a star deduction. But every now and then I have to tighten the screw something is not a problem. The mirror effect wertig, make no cheap impression (what one might expect from the super low price indeed). The mirror image is reduced significantly, but it offers a sufficiently large field of view. I have it mounted on my HPV trike, where they give a very good figure. Despite only 4 **** clear Kauftip for those who can tinker a bit (hose).
