Thin red fibre washers
 are a common sealing solution in plumbing, valued for their ability to expand slightly when exposed to water, which creates a secure, watertight seal. 
Key Features
Material: These washers are typically made from vulcanised fibre, a durable and resilient material made from chemically treated cellulose that is non-conductive.
Sealing Action: When in contact with water, the fibre material absorbs the fluid and swells slightly to fill any irregularities in the joint, enhancing its sealing performance in applications like tap fittings and pipe joints.
Durability: They are resistant to corrosion, oils, fuels, and mild chemicals, and can withstand temperatures from approximately -60°C to +100°C, providing long-lasting performance.
Thickness: "Thin" options are readily available, with common thicknesses including 0.5mm, 0.8mm, 1mm, and 1.5mm. 
Common Plumbing Applications
Tap Connectors: They are widely used with standard 1/2" and 3/4" tap connectors and service valves to ensure a tight seal.
Pipe Joints and Valves: Red fibre washers are ideal for sealing threaded connections in pipework and valves to prevent leaks.
Flanges: They are also employed in flange connections within plumbing systems and other industrial settings.