These self-lubricating IGUS high-precision bearings run whisper quiet and are used on LulzBot 3D printers. Little-to-no maintenance is required other than wiping the smooth rods occasionally.
(Standard) 8mm: HD-BU0013 RJM-01-08 Mini X (4 needed), Mini Y (4 needed), Mini Z (4 needed)
(Standard) 10mm HD-BU0001 RJM-01-10: TAZ 1-5 X (3 needed), TAZ 1-5 Y (4 needed), TAZ 1-5 Z (4 needed)
(Precision) 10mm HD-BU0030 RJMP-01-10: TAZ 6 Y (4 needed), TAZ 6 Z (4 needed)
(Precision) 12mm HD-BU0029 RJMP-01-12 : TAZ 6 X (3 needed)