SeaSure 25mm Treble Block w/Shackle

The SeaSure 25mm Treble Block with Shackle is a compact, load-bearing pulley system designed for sailors, anglers, and boaters who demand reliability in demanding marine environments. Whether you're rigging a sailboat, managing deck hardware, or setting up a fishing vessel's tackle systems, this marine-grade block delivers the mechanical advantage and durability needed for years of trouble-free operation on the water. The treble configuration allows for flexible rigging configurations, making it an essential component for both new builds and retrofit applications across cruising and commercial vessels.

Built with marine-grade stainless steel side plates and corrosion-resistant rivets, the SeaSure 25mm Treble Block features an arnite (engineered plastic) sheave that combines exceptional durability with minimal weight. The plain bearing design ensures smooth operation while the arnite sheave offers superior wear resistance compared to traditional wooden blocks, eliminating the maintenance headaches of rope chafe and sheave degradation. At just 1 pound, this block maintains strength without adding unnecessary topside weight—a critical consideration for vessels where weight distribution affects performance and fuel efficiency. The included shackle attachment simplifies integration into existing rigging systems and allows quick disconnection when needed.

Cruising sailors, commercial fishermen, and serious recreational boaters rely on SeaSure blocks for mainsheet systems, boom vangs, jib leads, and other critical deck applications where failure is not an option. The 25mm size provides an ideal balance of mechanical advantage and compact profile for vessels ranging from small sailboats to larger cruising yachts. This time-tested design has earned its reputation as one of SeaSure's best-selling ranges, proven through decades of real-world use in saltwater and freshwater applications. Installation is straightforward—secure the shackle attachment point to your existing rigging hardware and thread your line through the sheave for immediate load distribution.