Greenfield Vinyl Coated River Anchor 20 Lb. Royal Blue. The Tri-Fluke design of the River Anchor allows flukes to penetrate in soft and moderate conditions and 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. Designed to hold boats under 24'. Weights vary due to metal and coating content. Listed weights are approximate. Features of Greenfield Vinyl Coated River Anchor 20 Lb. Recommended Boat Size (in winds up to 30 Knots): Boats Package Contents: Greenfield Vinyl Coated River Anchor 20 Lb. Greenfield 520-R: Vinyl Coated River Anchor 20 Lb. Royal Blue