Aprilaire® Replacement Float Assembly, For Use With: Model 400, 400A and 400M Humidifier, Plastic, White, 1-3/8 in OD x 2-1/2 in L
The Aprilaire Float 4406 for Model 400. These float in the Scale Control Insert/Float Chamber to control the supply of water. When the water level is high enough, the right hand float turns off the water supply. As water evaporates and the float reaches the bottom, the electronic switch is activated.