Replacement Humidifier Pad #A04-1725-050 for Skuttle and Humidimatic Drum Style Humidifiers, 1-Pack.11" Belt-Type Pad for Drum-Style Whole House Humidifiers. This foam, belt-style humidifier filter is also known as the water or evaporator pad. The whole-house humidifier and the one humidifier part that needs regular replacement. Inside the humidifier, this rotating evaporator pad lifts water from the water pan into the air stream. The filter is constructed of a foam material that absorbs and holds water for evaporation. Features: OEM factory original part. Made in the USA with quality materials. Provides humidity to keep you comfortable during the dry heating season.