Details: New Pyramid Anchors seachoice 43920 Model 43920 Weight 150 lbs. Boat Size 18'-20' : Pyramid anchors provide excellent holding power and work in tidal waters and rocky or sandy bottoms. They are superior to concrete blocks because the anchor rapidly sets itself by presenting a digging edge to penetrate the bottom. The pyramid shape presents a large surface area which creates high suction that increases the deeper it sets. The short shank allows mooring in shallower waters without chain wrap-up a characteristic of mushroom anchors.