What surcharge is applied if a letter is enclosed in non-paper material?

The surcharge applied if a letter is enclosed in non-paper material is known as the non-machinable surcharge. This fee is imposed because non-paper items can interfere with the automated processing systems used by the postal service. When a letter is non-machinable, it means that it cannot be processed through the usual machines without requiring additional manual handling. This can include factors such as the physical dimensions, weight, or the materials used that demand extra attention or resources to ensure proper delivery.

In addition, the other options do not accurately represent the specific surcharge applied for non-paper materials. The oversized surcharge generally pertains to items that exceed standard dimensions, rather than specific materials. Fragile is not a category applicable for surcharges in the postal system; it refers more to the content rather than the packaging. Special handling is reserved for items needing extra care but isn't specific to the material used in the envelope or package itself. Therefore, the correct characterization of the surcharge for letters enclosed in non-paper material is the non-machinable surcharge, reflecting the operational shifts required to handle these items.