Pest Expert Formula ‘C’ Cluster Fly Spray is a fast-acting cluster fly killer with a long-lasting residual that helps maintain cluster fly control. Pest Expert Formula ‘C’ is the most powerful cluster fly killer spray available to the amateur market, offering both fast-acting and long-lasting cluster fly control to help you eradicate a cluster fly infestation in your home, loft or roof space. Formula ‘C’ Cluster Fly Spray should be applied to any alighting surfaces including window frames and roof timbers. Cluster flies will die on contact with the invisible insecticidal residue, which is effective for up to 12 weeks, offering extended protection from cluster flies. Formula ‘C’ is water-based and low-odour, making it perfectly suitable for use in homes with children and/or pets, provided they are kept out of the area being treated until all surfaces are dry (2-3 hours). The active ingredient in Formula ‘C’ is the powerful broad spectrum insecticide cypermethrin (0.1% w/w), which is also effective against a wide range of flying and crawling insects. Each one litre trigger spray is sufficient to treat an area of approx 25m2.