SeaSure 25mm Single Block w/V-Jam

The SeaSure 25mm Single Block w/V-Jam is a purpose-built marine hardware solution for sailors and boaters who demand reliable rigging performance in demanding saltwater environments. This single block pulley system has earned its reputation as one of SeaSure's best-selling ranges, trusted by cruisers, racing crews, and commercial operators for decades. The V-Jam mechanism provides secure, load-holding capability without slipping, making it ideal for mainsheet systems, traveler controls, and other critical deck applications where safety and dependability are non-negotiable.

Built from marine-grade stainless steel side plates and rivets, the 25mm block combines corrosion resistance with lightweight construction—critical for vessels where weight aloft matters. The sheave is crafted from arnite, a high-performance engineering plastic that is exceptionally hard-wearing and requires minimal maintenance in saltwater service. This material pairing delivers silent operation (no squeaking under load) while eliminating the noise fatigue that affects both crew comfort and on-water communication. The plain bearing design ensures smooth load transfer with predictable handling characteristics that experienced sailors rely upon when fine-tuning sail trim or executing demanding maneuvers.

This block suits cruising sailboats, racing yachts, and charter vessels operating in coastal or offshore conditions. The compact 25mm size makes it appropriate for mid-range sail plans and secondary control systems, while the V-Jam feature eliminates the need for additional stopper knots or complex rigging workarounds. Installation is straightforward on existing hardware: simply shackle or lash the block into position using standard marine attachment methods. Compatibility extends across most modern boom systems, traveler tracks, and deck hardware—verify your mounting points and line diameter (typically 6–10mm rope works best) before ordering to ensure proper fit and load capacity.