Needle rollers also use needles for skin resurfacing but are often too large and unwieldy for tight areas. They are also dependent on hand pressure, so the depth of penetration varies depending on the the amount of pressure exerted and the softness of the skin, while the Dermapen depth of penetration is set precisely with an electronic dial. There is also lateral trauma to the skin when the needles on a roller pull out of the skin as the wheel turns. This does not happen with the Dermapen, which relies only on vertical needle action