"The Cat Mate 210 Standard Cat Flap can be used in any single or double glazing glass panes, as well as in wooden or acrylic doors. The cat flap has a 4 way locking system and magnetic closure, making it easy for your cat to enter safely, while keeping out other stray or unwanted cats. Product dimensions: 245mm diameter, 223mm cut-out diameter. Circular shape. Available in white. A glazier may be required for installation into glass panes."