Twin Pillow Block Linear Ball Bearing IPPSWN08G 1/2" Open - Precision Plus Self-AligningTwin linear ball bearing pillow blocks, open shelled, with a 1 2" ID (inner diameter) crowned shell bearing inside an aluminum alloy housing. Part of the Precision Plus self aligning series, the IPPS twin bearings feature two grease zerk fittings, known as lubrication ports, located in the pillow block. Open shell design for use with rail supported round linear shafts Temperature Range: 4 +176F ( 20 +80C) Variant ID Sizes: Available from 1 4" to 2