INKA Cover Internal Corner Adjustable 90-135 Degrees TTI-IH123 123/72/145MM RAL9016. Open internal corner that covers the opening between two installation ducts that have been installed at an angle to each other. The corner piece consists of two parts that are adjustable to each other to create the required angle. Angle adjustment 90-135°. Protection class IP40 if the installation duct system is mounted directly on the wall. For TTI-IH123, the cover plate TTI-BP can be used to achieve protection class IP20 if the system has been installed using brackets. Material PC/ABS.