Apparatus and components in this class used in plants for the chemical and electro-chemical industry; scientific, nautical, surveying, electric, photographic, cinematographic, optical, weighing, measuring, signalling, checking (supervision), life-saving and teaching apparatus and instruments; apparatus for recording, transmission or reproduction of sound or images; magnetic data carriers, recording discs; automatic vending machines and mechanisms for coin-operated apparatus; cash registers, calculating machines, data processing equipment and computers; fire-extinguishing apparatus

High density polyethylene (HDPE) underdrain filter for sewage; underdrain filter for water purification by gravity or filtration; plastic water filtration apparatus for use in water purification plant; underdrain block filter for drinking water and desalination pre-treatment