Standard Size 4" - Coasters are standard size and fit into most glasses such as cups and Mugs, bourbon, highball, lowball, glasses, coffee mugs, tumblers, flasks, Mason jars, and large fountain drinks.Anti-Slip Backing Cork - These coasters have a non-slip backing and can also be used as a table protector. With these coasters on their side, they'll protect your surface from your spilled drink and protect their beautiful design against wear and tear.