The Forestay Extension is the part that feeds through the bow plate and screws into the turnbuckle. Furthermore, it’s what the 1/8″ Forestay attaches too. Note that this is a thicker forestay extension that requires an upgraded turnbuckle and Forestay as well, see below. These forestay extensions hold up the mast, and can eventually wear out. At the beginning of every season you should always check all of your rig. Especially, these forestay extensions.
Note: A loose rig rocking over time, even while the boat is on land is what causes forestay extensions to where out. A loose rig mast should be pulled forward by the jib halyard when not in use. This will prevent even the standard forestay extensions from wearing out.