For openings up to 9" x 3" (229mm x 76mm). Screw hole distance: 254mm x 76mm. Desgined to fully cover single brick aperture Integrated flyscreen to protect from flies, insects etc Suitable for external and internal use including larders, cupboards and wardrobes. Screws are concealed to provide a more attractive finish Hit & Miss design means you can open and close vent by sliding each way Meets building regulations. Please note it is not suitable for use with gas appliances. Screws are not included.