Résponse de l'équipe de Sport-Thieme:
Sorry for our late reply. Regarding the missing 4 pairs, there was a regular afterdelivery in the meantime. Could you give any further information about your critics with the general quality of the tubings or why you got difficulty to fix the grips with the tubes? Your help is much appreciated, as it is a patented locking system indeed. It is exactly the small “ball” integrated in the eyelet, that should block and prevent the fitness tube from slipping out. Would be really unusual, if this would not work. Maybe you can tell if the problem occurs only between the “Theraband-Tubings” and the grips – or between our Sport-Thieme Vario Tubes and the grips?