compositions of the type from which many commercial types of o ring seals are formed suitable types of synthetic rubber such as the buna type being preferred so as to be un affected by grease type lubricants for example in accordance with the principals of the invention the sealing effect of the lip seals 36 38 and 40 is augmented by employing a grease type lubricant which is introduced through passage 44 to the lubricant chamber 46 in accordance with the invention it is an important feature that when the grease referred to is delivered under pressure to the chamber 46 the pressure of the grease against the angularly extending flange 42 of lip seal 36 presses the terminal edge of the flange 42 tightly into engagement with shaft 16 and thereby prevents grease from passing between the flange 42 and shaft 16 into the area occupied by the bearing unit 24 however grease when under pressure can move against the flange 42 of the intermediate lip seal 38 and be forced between the terminal edge of said flange 42 and the shaft 16 outwardly toward the outer end of said shaft and thereby cause grease to be discharged into the smaller supplementary lubricant chamber 52 which is between the flanges 42 of the lip seal 38 and additional lip seal 40 such passage of the lubricant is caused by the pressure of the same expanding the inner rim of the flange 42 of lip seal 38 sufficiently to cause the grease type lubricant to move into the supplementary lubricant chamber 52 between seals 38 and 40 continued pressure exerted upon the grease in annular lubricant chamber 46 will also cause the inner rim of the flange 42.