SMSK20WUUE NB Square Flange Double wide Pilot End Slide Bush Anticorrosion Made in Japan:NB Linear Systems SMSK20WUUE NB Square Flange Double wide Pilot End Linear Slide Bush, The retainer material is steel, Bearing is anticorrosion, It is seals on both sides, series mainly used in the USA, NB brand (Nippon Bearing Linear Systems), Made in Japan.