Sedgewick rafter counting chambers are used for counting particles and microorganisms in 1 ml of water or other transparent liquids, among other things for drinking water analysis. The counting chambers are made of high-quality optical glass with a chrome grid (counting net). The cell = 1 cm³ is graduated with a 1mm grid that divides 1 ml into 1000 μl.

Glass counting chamber with chrome grid for phase contrast with ground and faceted edges, including cover glass.