RK 520 GXW XW-Ring Chain - 120/Gold Chains feature quad-staked pin riveting, solid rollers and solid bushings, They are all pre-stressed and pre-stretched for better performance with fewer adjustments XW-Ring Sealed Chain GXW are the leading edge XW-ring features a Nitrile Butadiene composite construction with 6 sealing points and 3 lubrication pools The Nitrile Butadiene composite is oil and contaminant resistant creatinga barrier to keep lubricant in and contaminants out 100 percent longer wear life than basic O-ring chain