Item Type: Aluminum Profiles Spacer Block Material: Nylon Model(optional): 2020 or 3030 or 4040 Use: Fixed Application Description: Insert the end of the connection block into the groove of the profiles at a right angle, and then fix it tightly to the profiles after 90 degrees of rotation. Then you can install other types of inner plates such as plexiglass on the profiles, and lock it with bolts for simple installation and removal 20 Size: Approx. 13.7 x 15.7 x 15.7mm or 0.5 x 0.6 x 0.6in 5.7 x 10mm or 0.2 x 0.4in 5.25 x 1.8mm or 0.2 x 0.1in 30 Size: Approx. 20 x 20 x 17.5mm or 0.8 x 0.8 x 0.7in 14 x 8mm or 0.6 x 0.3in 2 x 12mm or 0.1 x 0.5in 40 Size: Approx. 23 x 18 x 25mm or 0.9 x 0.7 x 1in 8 x 16mm or 0.3 x 0.6in 4.5 x 13mm or 0.2 x 0.5in Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.