Do not buy this dimmer. It is junk. I have two of them that didn't even last two years.
The slider arms are underbuilt, and the plastic button ends are hard plastic. Either the slider arm breaks off or the knob end splits into little pieces.
The detent for the off position on the lamp is too stiff, which makes the arms/knobs break faster. The detent gets harder as time goes on. One of mine cannot even be turned off, even after spraying electronic lubricant in it.