L Size: outer frame: 33 x 44cm, inner door flap: 28 x 33cm. S Size: outer frame: 25 x 31.5cm, inner door flap: 21 x 24.5cm. The pet door is made of high-quality material, wear-resistant, temperature-resistant, and designed for long service life. Comfortable for daily use: ideal for balcony doors, allowing pets independent access without requiring owners to repeatedly open the main door. Provides a separate entrance for pets while maintaining the functionality of the fly screen door, offering protection from mosquitoes and insects. Features automatic closing with magnets in the bottom frame. Lightweight design allows easy passage for pets. Includes locking mechanisms on both sides to fully secure the door and control pet access. Suitable for installation on fly screen doors, windows, and similar screened areas. Installation instructions included for easy setup. Note: inner flaps do not include grille; the cut-out grille must be installed into the frame during setup.