A brass pipe screen, often referred to simply as a "screen," is a small, usually circular piece of metal mesh made from brass. It is used in smoking pipes, particularly in tobacco pipes and certain types of water pipes (such as bongs), to prevent the inhalation of ash, debris, or other particulate matter when smoking. The number "5" you mentioned is not standard terminology for brass pipe screens and does not have a specific meaning in this context.

Brass pipe screens are typically placed at the bottom of the bowl or pipe chamber. When you pack your smoking material (tobacco, herbs, or other substances) into the pipe, the screen acts as a barrier, allowing air to pass through while keeping larger particles from being inhaled. This helps to ensure a smoother and cleaner smoking experience.

If you have any specific questions or need more information about brass pipe screens or related topics, please feel free to ask.