These are the Birch brand aluminium self cover button shells with sturdy solid plastic shank backs. Bulk pack of 100 self cover alluminium button shells and plastic backs with shank. Buttons are 12mm diameter. The smallest in the range. No sewing needed. The tool shown in photo is NOT included in pack. You will need to purchase seperately if you dont have one. These buttons with sturdy plastic shanks are perfect to use with thin elastic hairties or for sewing only. YOU NEED TO ORDER AN ASSEMBLY TOOL MADE FOR PLASTIC BACKS, THE OTHER TYPE DON'T WORK WELL WITH PLASTIC BACKS.