The Filter 15 Strainers are designed to remove unwanted particulates from a liquid or gas. The key difference between strainers and filters are the size of the particles they remove. Strainers typically remove larger particles that are visible in a liquid or gas, while filters remove contaminants that are often so small, they cannot be seen with the naked eye. The Filter 15 Strainers can be defined as a pipe fitting through which liquid is passed for purification, filtering or separation from solid matter.