This is a standard Wheaton 300mL BOD bottle with a heavy coating of black PVC plastic that blocks all visible light up to 800nm. This inhibits the production of oxygen by algae. This bottle is recommended for use in marine photosynthesis projects in which you need to compare oxygen in a light and a dark bottle. This bottle is supplied complete with a glass robotic stopper and an opaque black cap. Diameter x Height: 73 x 167mm.