The Oxoid Anaerobic Indicator BR0055 consists of a cotton strip impregnated with a redox indicator solution enclosed in a laminated foil envelope. This formulation and a pure cotton strip gives a reproducible redox colour change in a shorter time than similar products that are available. Use of the Oxoid Anaerobic Indicator will support the evidence of pressure changes which occur with active catalysts and ensure that any absence of growth does not reflect poor anaerobic incubation.