Hello There, I have renewed 21 window while leave installing new exterior blinds at our house 3 years ago. The craftsman has built the Gurtwickler of Schellenberg. So far, I already had to replace 3 Gurtwickler because of the roll-up mechanism decreases, ie the spring force of the steel strip in the winding unit does not last very long. Unfortunately Schellenberg has not responded to the two messages I have written about it. I'm going to gradually replace the defective products from other manufacturers by Gurtwickler and if necessary also to spend more money on it.
