Features: 3. Thread: M6 Suitable for industrial aluminum frame structures, 3D printers, CNC routers, robot projects, woodworking machinery, aquariums, etc. 4. Made of zinc alloy with nickel plating on the surface, it has high hardness and long service life. 5. The L-shaped hidden angle bracket is used to establish a right-angle connection between two aluminum profiles. Insert both ends of the L-bracket into the profile's grooves and then tighten the set screws to secure the two profiles. 6. Built-in connection design, beautiful and simple. Suitable for 4040 series aluminum profiles with 8mm slot. Note: Easy to install with set screws and wrench. Specifications: Material: Zinc Alloy Color: Silver Brand: BQLZR Size: Length: 49 mm/1.93 inches Width: 9 mm/0.35 inches Height: 49 mm/1.93 inches Hole distance: 16x16 mm/0.63 inchesx0.63 inches Weight: 63 g Package includes: 4 x L-shaped inner joint bracket