lower turn off path 312 of the former end cover 3 then continues to travel along the tilted turn off path 313 of the latter end cover 3 thereby making an upwards turning and returns to the upper turn off path 311 of the former end cover 3 such an endless circulation of the ball 5 between the slide rail 1 and the slider 2 will be maintained as long as the linear guide way operates it emerges from the above description that the ball circulation system for linear guide way according to the present invention in which the cross wise and separated circulation passages are integrally combined together by the end covers 3 is apparently more advantageous than one in which the two circulation passages are segregated as in the conventional techniques in several respects namely 1 the two independent circulations combined in one piece only needs twice operations to fill the rolling balls resulting in facilitating assembly work 2 rolling balls 5 are able to make up and down circulation and uniformly lubricated with a simply constructed oil circulation path 3 up and down circulation of rolling balls 5 causes reducing their load stress the lengthened circulation passage allows to accommodate more rolling balls 5 in the linear guide way further contributes to reducing their loading stress in addition for further variation of design aspect for the end cover structure some of the extra design features are added for the end cover 3 in a first embodiment shown in fig9 the oil path 315 formed on the main block 31 is replaced by an oil path 324 formed.