Polyform A-4 Buoy 20.5" Diameter - WhiteA 4 Buoy 20. 5" Diameter White The A Series is the product that launched the Polyform story. This all purpose product, with the signature "blue ropehold" has proven itself in the most adverse conditions. Marking gear used in heavy seas is no easy task. That's why more fishermen use Polyform A Series than all other buoys combined. You name it, ocean, sea, or river, and the A Series has been there. Put your trust in Polyform's most versatile and well