Anti-bacterial treated, traps minerals. Replacement filter fits most Holmes humidifiers. Metal reinforcement. Adds rigidity to shape of the wick filter when moistened. Also adds stability with today softer, more absorbent paper. Prevents slumping or insagging in over time or when wet. Helps maintain the humidifier designed output. Wick filter fits Duracraft DCM-200, DH-888, 890, 890C DCM-891B, 891S (AC-888), Honeywell HCM-890, 890B, 890C, HCM-890-20 (AC-888), Touch Point S35E-A.