650SS vs 6500SS Design Changes Install Note: Handle Pivot Diameter Increase on 6500SS Original 650SS uses 15B and 15BL pivots which are thinner in diameter than the 15G used on the 6500SS. The 15G is also right / left reversible eliminating the need to have 2 separate pivots. This is accomplished by having 2 different sets of threads on the same pivot. One cut clockwise, and the other cut counterclockwise. This is also one reason (besides added strength) – that the diameter had to be increased; to allow for the multi-thread / multi tube O.D. design. Increasing the diameter of the handle pivot means that the main gear shaft diameter must also be increased to accept the thicker pivot screw. Also, since the main gear shaft seats into ball bearings on each side, the dimensions of the ball bearings used must also be changed. Finally, since the ball bearings sit inside the housing one side, and the housing cover on the other side, the holes for the bearings in those parts must also increase in size. In summary, main gears and main gear bearings are not interchangeable between 650SS and 6500SS, unless you also change the housing, housing cover, #20 bearings, and handle pivot. What to expect from Fishgrain? prompt service items always as described smooth and accurate transactions excellent packaging effective and fast communication I like helping and making people happy with fishing tackle. -JG Helpful Tips Use ' add to cart ' button when purchasing multiple items This will combine your items into a single checkout with (1) shipping charge Use ' see other items ' link to search Fishgrain inventory Contact me anytime with questions or concerns of any kind I am happy to help you with anything fishing related Thank you .... all orders are sincerely appreciated