The unique property of a fibre tap washer - sometimes referred to as vulcanised fibre washers - is that the material naturally expands when it becomes wet. In theory (and often in practice), this helps it to perform more effectively as a sealant. Widely used in many areas of plumbing, fibre washers tend to be somewhat easier to compress than rubber or nylon versions. This can mean that they are at less immediate physical risk of damage from over-tightening, potentially leading to a longer lifespan depending on the tap type and how it’s used. This 15mm washer is for use with both hot and cold water and in all standard basin and sink taps. Loose per each.