This Hub Mount Winch Pulley is able to fasten to any hub or component which possesses the 16mm hub pattern. The pulley is considered a 'dual spool', meaning it is divided in the middle so you can wind two separate strings independently of one another. Typically one string is wound the opposite direction of the other so that, as the pulley rotates, it lets string out on one side as it winds the string from the opposing side in. This pulley is excellent for creating a power retract in a linear motion setup such as the Cascading Kit for 1121 Series Low-Side U-Channel. To fasten string to the pulley, there is a hole in each side of the pulley to run the string to and tie a knot on the inside to keep it from pulling out.