The Hydrasand 5" Foam Backer Pad (Part #AS003500) is a replacement accessory designed for the American Sanders HydraSand Multi-Head Sanding Disc system. It attaches to the bottom of the 5" pad drivers on the satellite assembly to provide a cushioned interface between the driver and the abrasive disc. The primary purpose of the foam backer pad is to soften the sanding action, resulting in a smoother finish on wood floors. By adding cushioning, it helps eliminate "pigtail marks" (swirl marks) often left by aggressive sanding. The pad is removable; taking it off increases the aggressiveness of the sanding disc, allowing users to toggle between fine finishing and heavy material removal depending on the project phase.