TW24UU:TopBall:Made in Japan: High Load Standard type:NB Linear Systems Self Aligning Ball Bushing TW24UU 1 1/2" Bore High Load Standard type TopBall inch type linear motion ball bushings/bearings, inner diameter(bore) is 1 1/2" inch dimensions with built-in seals, the Topball slide bush is a high performance bushing with three times the load capacity, capable of providing up to 27 times normal travel life of a conventional slide bushing. high accuracy grade linear bushings, series mainly used in the USA, NB brand (Nippon Bearing Linear Systems), made in Japan.