Greenfield Products Coated River Anchor - Red The Tri-Fluke design of the River Anchor allows the flukes to penetrate the river bottom in soft and moderate conditions, or to engage rocks and structure in rivers and current. The River Anchor is a great all purpose anchor for lighter craft, or a great second anchor. Larger models are preferred choice for pontoon boats and other difficult to hold boats. Weight Boat Size Recommended Chain Size Scope 16 Up to 18 14 x 4 51 20 Up to 24 14 x 4 51 30 Up