TWD16WUU NB Type:Slide Unit Pillow Block Made in Japan:NB Linear Systems Nippon Bearing Linear Systems 1" Slide Unit Pillow Block (Inch Series), the innerdiameter(bore) is 1" inch dimensions with steelretainer, bearing is a high accuracy grade linear bushings,series mainly used in the USA, NB brand (Nippon Bearing Linear Systems), made in Japan.