Free running sheaves are critical for easy operation of your sailboat. If sheaves become dirty or seize, you may find it difficult to raise your sail, or sheet in. Replacement sheaves are available from Harken, Ronstan and Dwyer. These sheaves are used in a wide variety of settings, from mastheads to on blocks. If you don't find the exact match, contact us and we will help you find a replacement sheave that will work. One of the most important things is to consider the working load of your sheave. Make sure that when you purchase a replacement that the working load fits with your purpose.