Twin Roller Pillow Block Bearing TWN-24-OPN-SCP 1.5" Shaft DiameterChrome Plated Twin (TWN) Roller Pillow Block Bearing for a 1. 5" Diameter Shaft. Twin pillow blocks cover twice the space on a linear shaft as a single version. This open linear bearing pillow block has two sets of 3 opposing roller bearings mounted on this double sized twin housing, as if two Single Roller Pillow Blocks (SPB) were fused together to make a much larger bearing. This differs from the Double (DPB) Pillow Blocks which also have 2 sets of