Attribute These single D-Shape shelves come with steal bearings and are available in a 20", 28" and 32" diameters.LD-4BW-201-20SBS-1 (1) Shelf with steel swivel bearing attached 5/8" thick maple tray bottom Laminated hardwood rim Limited lifetime warranty Single 20" Banded Wood D-Shape ShelfLD-4BW-201-28SBS-1 5/8" thick maple tray bottom 7" Steel BearingLD-4BW-201-32SBS-1 (1) Shelf with steel swivel bearing attached 2" banded wood rim 5/8" thick maple tray bottom Laminated hardwood rim Limited lifetime warranty Single 32" Banded Wood D-Shape Shelf