Twin Pillow Block Linear Ball Bearing IPPSW24G 1.50" Closed - Self Aligning Precision PlusTwin Linear Ball Bearing Pillow Block, closed shell, with a 1. 5" ID (inner diameter) bearing inside a housing made of aluminum alloy. It is self aligning due to a crowned bearing shell inside the housing. The twin IPPS products all come with 2 grease zerk fittings, a small holes in the pillow block which are also called a lubrication ports. Twin Double size equal to two standard bearings mounted back to back Temperature Range: 4 +176F ( 20 +80C)