Please note that for the V3100 you will "flatten" the filter out. The original filter is also a round filter. Humidifier Filter Compatible with Protec WF2 Extended Life Vicks WF2; Compatible with Vicks V3500N, V3100, V3900 Series, V3700, Sunbeam 1118 Series & Honeywell HCM-350 Series; This is a high quality replacement part. By LifeSupplyUSA. By LifeSupplyUSA. Any brand names or logos are the registered trademarks of their respective owners. Any use of any brand name or model designation for this product is made solely for purposes of demonstrating compatibility.