Fortress Marine Anchors 4lb Anchor f/16-27' Boats. In the US Navy tests not only did the Fortress out-perform heavier steel anchors they were also able to withstand pull loads that averaged over 200x their own weight.Fortress Anchors are constructed using a high-tensile corrosion-resistant aluminum magnesium alloy. This results in a lighter easy to handle anchor with superior holding power.The anchors have been designed to be easily disassembled for compact storage or as a spare and/or a storm anchor. All Fortress Anchors are precision-machined for sharpness and quick penetration into common sea bottoms which ensures faster setting-performance. Specifications for Fortress Marine Anchors Anchor: Manufacturer: Fortress Marine Anchors Color: Silver Fabric/Material: Aluminum Alloy Features of Fortress Marine Anchors FX-11 7lb Anchor f/28-32' Boats Weight (lbs): 7lbs Boat Length - Max (Feet): 28-32' Construction: Aluminum Alloy Package Contents: Fortress Marine Anchors Anchor Fortress Marine Anchors FX-7: 4lb Anchor f/16-27' Boats FX-7