SMSKC6UU NB Center Mount Square Flange Slide Bush Made in Japan:NB Linear Systems Nippon Bearing Linear Systems SMSKC6UU NB Center Mount Square Flange Linear Slide Bush, The retainer material is steel, Bearing is seals on both sides , Bearing is anticorrosion, series mainly used in the USA, NB brand (Nippon Bearing Linear Systems), Made in Japan.