SM12GUU-OP Type Open Seals on Both Sides: Slide Bush Made in Japan:NB Linear Systems Nippon Bearing Linear Systems SM12GUU-OP Linear Slide Bush, bearing is open, It is seals on both sides, it is Retainer material is resin, bearing is a high accuracy grade linear bushings, series mainly used in the USA, NB brand (Nippon Bearing Linear Systems), made in Japan.