its a snap ring, and from what i have seen they dont come seperately, go back and tell the place you bought it from that your axle didnt come with one and they will give you one from another axle...............
or you have the wrong axle.........this happened to me before from car quest!
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10.02@149.5 Bullseye Power Turbos
Top Dead Center Performance
Mobile Alabama 251 661 6067
owner/operator
www.tdcperformance.net