Side in 5mm thick spruce plywood measuring 20x20 cm for the yarn ball container as seen on the Countrymammy Youtube channel. The stitching holes have a diameter of 1.5 mm and retain the closure so that you can choose whether to open the hole or leave it closed depending on the project you wish to make. Wood is a living material and may warp slightly depending on temperature and humidity conditions. Made with 100% ecological material and engraved with 100% renewable solar energy. Excellent choice!