SW4GAJ:Clearance Adjustable Type Ball Bushing Made in Japan:NB Linear Systems 1/4" SW4GAJ Clearance Adjustable Type Linear Motion Ball Bushing, 1/4" Bore inch type linear motion ball bushings/bearings, inner diameter(bore) is 1/4" inch,high accuracy grade linear bushings, inch series is mainly used in the USA, NB brand (Nippon Bearing Linear Systems), made in Japan.