MSRP: $67.99* (pack of 6) Spine Inside Diameter Outside Diameter GPI 300 0.2445" 0.296" 9.1 350 0.2445" 0.293" 7.9 400 0.2445" 0.291" 7.4 500 0.2445" 0.286" 6.3 4538 2615 8043 0016 0719 8390