NB SW4 1/4 inch Ball Bushings Linear MotionNB Systems SW4 1 4" inch Ball Bushings Linear Motion SW4: Made in Japan: NB Linear Systems Nippon Bearing Linear Systems SW4 1 4" Bore linear motion ball bushings bearings, inner diameter(bore) is 1 4" 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. Item Number of ball circuits Dimensions(Inches) Eccentricity radial clearance