TOOGOO(R) 520H Master Connecting Link O Ring Connecting Master Chain Link Gold Split/Clip for 520H DID 520 VX2 High Quality Material. Easy Installation. Precise Forging process leads to a stiff chain for better acceleration and more efficient engine work. Lightening hole allows for a lighter chain without compromising strength while removing mud and dispersing heat more efficiently. Improvement in transmission efficiency. Special pin with holes in both ends allow the chain to be lightened. Edge-cut inner plate reduces friction and allows for smooth engagement with sprocket.