TWA6WUU Pillow Block Slide Unit Nippon Bearing (NB) Linear Systems Made in Japan 3/8" Double Wide Block, Slide Unit Pillow Block (Inch Series), the inner diameter(bore) 3/8" inch dimensions with steel retainer, bearing is a high accuracy grade linear bushings, series mainly used in the USA, NB brand (Nippon Bearing Linear Systems), made in Japan.