The Pest Expert Formula ‘P’ Cluster Fly Smoke Bombs are a fumigation device for eradicating cluster fly infestations in your home or loft and an essential part of any cluster fly treatment. The Formula ‘P’ Fumer is a cluster fly killing smoke bomb which releases an insecticidal (permethrin) smoke and is ideal for getting rid of cluster flies in lofts, roof spaces or other areas of the home. One smoke bomb will treat a room of approx 6m x 8m (standard ceiling height) and one twinpack should be sufficient to eradicate a cluster fly problem in a standard roof space in a 2-3 bedroom house. To treat a cluster fly infestation in a larger loft area or several rooms add extra Fumers as necessary. Contain Permethrin at 13.25% w/w.