SWF20W NB:Made in Japan:NB Linear Systems Round Flange Double Widee Type Nippon Bearing Linear Systems SWF20W NB 1-1/4" Bore linear motion ball bushings/bearings, the inner diameter(bore) is 1-1/4" 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 Japa