Please do not nail it on the concrete wall.Specification: Color: Wooden/Multicolor Material: Wood, Metal Pin Length: 8.5mm / 9.5mm Open Width: 6mm Overall Size (L*H): 35 x 19mm / 35 x 20mm Package Contents: 20Pcs x Push Pins Advantages: The push pins are composed of wooden and metal, sturdy and durable, lightweight and portable, which are not easy to deform. Helps you to organize your desktop or your desk drawer well sorted, and is convenient for you to carry and store. Instruction: Push pins are practical for easy insertion and smooth for easy removal. Notice: Please do not nail it on the concrete wall.