Ultra light main gear shaft of ABU 1500C, 2500C made of extra strong duralumin (ESD), to remove 7g weight from the part. Fits to old ABU 1500C, 2500C, 3500C reels, with mechanical ratchet. Not fit to 1600C or 2600C thumb bar clutch models, or newer IAR instant-anti-reverse models. 3.5g. Genuine brass shaft 10.3g. Clutch return posts are increased from 2 to 4, and you may return clutch faster.