SMS50GUU Stainless Steel Anticorrosion: Slide Bush Made in Japan:NB Linear Systems Nippon Bearing Linear Systems 50mm Stainless Steel Anticorrosion Linear Slide Bush, The retainer material is resin, It is seals on both sides, SMS50GUU bearing is a high accuracy grade linear bushings, series mainly used in the USA, NB brand (Nippon Bearing Linear Systems), made in Japan.