An adjustable spacer with hardened end portions and a non-hardened intermediate portion therebetween is mountable between a pair of roller bearings also mounted on a shaft such an axle or spindle or the like. The hardened material contacts the faces of the roller bearings but helps prevent wear therebetween and unwanted movement of the bearings on the shaft. The unhardened material allows the spacer to collapse in the axial direction to maintain desired axial loads on the bearings.