Made from high-quality, material with an upgraded filter design to both filter large particles and maximize moisture output Upgraded Blue Pre-Filter Layer - Our premium upgraded blue layer pre-filter helps reduce the quantity of large particles circulating in your air Tips For Daily Use - For results, flip your T filter daily and only fill humidifier tank with distilled water. Hard water degrades filters and yellows them prematurely Installation Instructions - Soak your replacement wick for T Filter for humidifier HEV615 and HEV620 in cool water before replacing to uninterrupted moisture output. Place in filter housing with blue layer facing outwards (towards you) Type: Humidifier Filter Model: for HEV615 HEV620 HFT600 colour:Blue+white Material:Wood pulp paper size:20 x 16.5cm Package Contents: 4 x filter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.