Hobie - Mast - V2 Standard - Threaded - 81163001 Mast is designed for Hobie V2/GT Standard Fins only V2/GTT drives have threaded Hobie sprockets This is for the shorter ST fins, do not buy if you have the turbo fins Will not fit the MD180 drives, only the GT and earlier drives Doesn't fit V1 Mirage drive sprockets, those have a set screw