Please read the profile before purchasing. These items were passed down to me, so please refrain from purchasing if you are sensitive to imperfections or seek perfection. I do not know the exact materials. They appear to be 20mm x 45mm. 20 pieces + 1 piece The hardware with the moving line in the middle is called a "moving kan" (moving fitting), and is also known as a "ruck kan" (rucksack fitting) because it is used on bags, backpacks, etc. Usage: This hardware is mainly used to adjust the length of the shoulder straps of bags. Unlike plastic, it is strong, and the silver color makes it easy to match with any material. Thank you for your consideration ( •̀ᴗ•́ ) ̖́-