Note: Please ensure you have a survey carried out by a qualified Corgi registered gas installer to ensure the compatibility of your chimney / flue or intended location for a powerflue version, before making any purchase to avoid disapointment. This fireplace requires a class 1 chimney, class 2 prefabricated / precast flue or powerflue for homes with no chimneys, depending on the model you select. The above fires do not normally require additional ventilation in the room. The above dimension "G" refers to the rebate size which is adjustable by removing the detachable infill on the surround taking it from 25mm - 75mm (the rebate size is the depth available within the surround should there not be sufficent depth in the wall). For more detailed information about this product or to enquire about your nearest dealer to view this fireplace before making a purchase visit www.agnewsfireplaces.co.uk or click on the heading "Customer Services" at the top of this page, click brochures and scroll down to Agnews Fireplaces and click on the link to their website where you can also request a brochure to be sent directly to you if required