This bracket is quite handy, but has a design flaw. The upper part, in the locks the Navi, separates easily from the lower part, which is connected to the bicycle. In order to eliminate these design flaws, you have to drill and fix a bolt from the bottom in the holder. Then the device is fairly well usable. The Navi can be further separated from the bracket with a handle. It does not happen again that the valuable Navi lands on the tarmac, just because the road is bumpy.
