Use these for silky smooth Z motion. I can't stand the self aligning linear bearings, as they are simply bushings that windup binding. LM10UU Linear Bearings are widely available online. I was able to find a set of four with free shipping for $14. Snap rings hold the bearings in the mount, I sourced locally at ACE.
My basic settings:
.2mm Layer Height
Two files attached:
REV3 have the screw holes in the center of the part that can be used for the top mounts, but sacrifice some Z-Height.
REV4 have the screw holes in the top of the part can be used for the both the bottom and top mount. I'm currently using this setup.