SW6UU Seals on both sides NB Nippon Bearing Linear Systems Made in Japan SW6UU 3/8" Bore linear motion ball bushings/bearings, SW6UU is Seals on both sides, inner diameter(bore)= 3/8" inch dimensions with steel retainer, bearing is high accuracy grade linear bushings, series mainly used in the USA, NB brand (Nippon Bearing Linear Systems), made in Japan.