Can be used on both sides. There is a rubber insertion opening. You can also replace the rubber yourself. Width: Approximately 17cm Height: Approximately 9.5cm There may be small specks or lines of cotton residue, which is a characteristic of the fabric. Please understand that this is part of the fabric's texture before purchasing. The color of the actual product may differ slightly from the image. This is a handmade item by an amateur. There may be some errors, distortions, and misalignments. Thank you for your understanding and consideration. Shipping will be done using recycled materials and simple packaging. Thank you.