Manthorpe Brown 9" x 3" Air Brick Vents Pack of 20 Plastic interlocking air brick ventilator. Part number: G930. Provides 6,450mm² of airflow per 9" x 3" airbrick. Clip together facility provides a choice of ventilation sizes. Can be stacked together to create 9" x 6" and 9" x 9" combinations. Additional G935 extension sleeves available in menu options. Moulded in mortar key ensures secure adhesion to the building fabric. Meets NHBC requirements for the control of condensation in buildings. Manufactured to BS 493:1995 + A1:2010. Other colours and ventilation fittings for this product available in our shop.Use Air bricks to can also used in conjunction with the telescopic underfloor ventilator for providing ventilation below suspended ground floors. Air bricks to be used in conjunction with cavity sleeves for ventilation through external walls to a building interior.Features & benefits Air Brick (1201ab) equivalent area 6450mm² per unit. Unique stepped front grille greatly reduces the entry of wind driven rain. 6.5mm wide front grille openings comply with BS 5440 Pt 2 and British Gas requirements. Integral clip together facility allows multiple airbricks to be stacked to form 9”x 6” and 9”x 9” sizes. Available in a range of colours to blend in with various brick types. Very tough and robust. Durable and totally resistant to decay.Quality Satisfies all NHBC Standards 2008 Edition. Manufactured to BS EN ISO 9001 : 2008. Complies with all relevant Building Regulations. Meets all relevant British Standards. ‘Equivalent Area’ tested by BRE to BS EN 13141-1:2004.