"SETMASTER-NO 3 BEARING AIR SEAL,FORWARD SNAP DIAMETER; USED TO PRE-SET PWA72504 GAGE TO ZERO PRIOR TO USE; ALSO USED FOR TO VERIFY THE INTEGRITY OF THE HYDRAULIC CHUCK DETAIL OF PWA72489 MACHINING FIXTURE DURING SET UP; INNER DIAMETER: 5.60125 IN; TOLERANCE: PLUS 0.00025 IN; OV DIA 8.0 IN; HT 1.5 IN; WT 2 LBS"