AAI Graphite Rails for Uneven BarsAAI Graphite Rails for Uneven Bars are nearly unparalleled in their performance. What's the difference between the Graphite X and Graphite E Rails? There are two different kinds of AAI Graphite Rails for Uneven Bars available: Graphite E Rails these rails are "softer" and more flexible than the Graphite X Rails Due to their higher range of flexibility, Graphite E Rails can only be used with cabled equipment Made with less graphite strands, making it