15x15 mm system for square round tubes from DIY store Inside Dimension = 15.5 * 15.5 mm Nut Size M5 Nut internally Easily printable. For the framework are 0.8 mm shell and 25% filling enough. 15x15 mm system for square round tubes from DIY store Inside Dimension = 15.5 * 15.5 mm Nut Size M5 Nut internally Easily printable. For the framework are 0.8 mm shell and 25% filling enough. 15x15 mm system for square round tubes from DIY store Inside Dimension = 15.5 * 15.5 mm Nut Size M5 Nut internally Easily printable. For the framework are 0.8 mm shell and 25% filling enough. Strengthen the case of large forces. For aluminum hollow section profile is the weak point. Tighten the screw only slightly. For aluminum hollow section profile is the weak point. Tighten the screw only slightly. For aluminum hollow section profile is the weak point. Tighten the screw only slightly.