Approximately 1.1 to 1.2 cm in diameter. This is a set of 5 back buttons. (These are change buttons for student uniforms, with a black plastic base and a cherry blossom mark, used to fasten the buttons from the back.) Replacing the back buttons is easy, even for children. The 5 back buttons will be placed in a pouch and sent via Japan Post's Mini Letter service in simple packaging. There is no tracking number, so you cannot track the package. There is also a listing that uses Yu-Packet Post Mini, which allows for tracking. Please search for the product name: "Back Button, Standard Student Uniform - Black Plastic, Cherry Blossom Change Button Set of 5, New". Delivery will be by postal drop-off, not hand delivery. Items for which payment is confirmed by 12:00 noon will be shipped the same day. (There are basically no days when we cannot ship, but if there is an urgent matter that prevents shipping, we will ship the next day.) Depending on your area, delivery usually takes 1-3 days after the shipping date, delivered to your mailbox. For more details, please check the estimated delivery time from Osaka for Mini Letters on the internet. *New product. *Free shipping.