This is a new 520x88 drive chain for your 1989-1992 Polaris 250 4x6 Big Boss. This is a non o-ring style chain designed to correctly replace your oem chain and it comes complete including the masterlink and keeper. We also offer replacements sprockets so be sure to check them out in our selection. We'll gladly ship them with the chain to save on shipping costs. We offer new drive chains and sprockets for most atvs so be sure to check out our other items.