The bottle trap is an essential element of the basins plumbing that keeps the bathroom hygienic and clean. When we use the basin, the used water goes through the basin waste, into the drainage pipe and then into the sewer. Lot of other waste and dirt is accumulated in this sewer and naturally the accumulation causes a lot of harmful gases. These gases need an outlet and that, they get through our drainage pipes, through the wastes and back into our bathrooms.Here is where and why you require those basin bottle traps. The bottle trap prevents these gases to enter the bathrooms, thus helping maintain hygiene in the bathroom and keeping it safe for us.- Material: chromed brass; - Main diameter: 5/4" BSP x 32mm.