Replacement tubes for the following Grolux 2ft Tube – 590mm long 18 Watt Grolux Fluorescent tube Grolux 4ft Tube – 1200mm long 36 Watt Grolux Fluorescent tube Tube glows purple Promotes great vegetative plant growth For seedlings, cuttings and lighting of fresh water aquariums Recommended for greenhouses, indoor gardens and florists.