Lutron NF-20 fluorescent dimmers for use with magnetic ballasts (generally cannot be dimmed effectively below 20 percent). For best performance and reliability, Lutron recommends using Hi-lume or Eco-10 dimming ballasts. 277V Single pole, slide-to-off dimmer with wall plate. The original smooth linear slide dimmer. Large control. Heavy duty components for surge protection and long product life. Power failure memory.