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 and exit for pets while maintaining the functionality of the fly screen door, offering protection from mosquitoes and insects. Features magnets in the bottom frame for automatic closure. 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 other screened areas. Includes installation instructions for easy setup. Inner flap does not include a grid; users must install the cut-out grille into the frame during assembly.