Used Extension (Mast Base) This is a set of a NEILPRYDE MAST BASE 45 and a joint. Because it's a long extension, it can cover even if the mast is short. Ideally, you'd have a mast specified for the sail, but I used this when I didn't have one. Example: Even if the sail's mast specification was 460, I would rig it with a 430 mast and this extension.