Sixity 2012 Polaris 900 Ranger RZR XP 4X4 Rear Left Axles Back Driver R12XT87AA 9EAS RZR 4 XP Complete Side Note: R12XT87AA 9EAS RZR 4 XP. Axle arrives fully assembled and ready for quick and easy installation. Severe-duty OE replacement ATV/UTV axle designed for extreme off-road vehicle applications. Precision ground internal components, engineered to provide superior performance. Manufactured under ISO/TS 16949 and ISO 9001 Quality Standards to OEM dimensional specifications to ensure vehicle fitment and product reliability. Made from 4340 chrome-moly steel bars, providing an exceptional strength-to-weight ratio. Durable and long-lasting. Neoprene boots provide superior flexibility, puncture-resistance and environmental protection compared to thermoplastic boots. Internally lubricated with high temperature/high load bearing moly grease.