Two-piece connecting links (aka couplers and also known as couplers or hammerlocks) are a very common rigging component. They are used extensively in building chain slings, often used to connect the chain legs to the top master link. These particular couplers are a very important part of Pewag's Grade 120 Winner Pro chain system. That's because all of Pewag's fittings feature an eye rather than a clevis pin, so you need these coupler to attach the components to the chain itself. They can also be used to connect other rigging components together, such as hooking shackles to chain slings, or connecting eye bolts to round rings. Assembly is quick and easy, just like other two-piece couplers...simply drive in the pin with a hammer, or drive it out with a punch if you need to take the coupler apart. Made from Grade 120 alloy steel. Powder-coated blue for corrosion protection. Safety factor of 4:1.