The original Series IV rockers of 2000 maintained the same mission as the predecessors, to fit the OEM head without modifying it, except the valve cover -- which on this set was required. They are the strongest, lightest, most high tech versions of the Miller BOSS rockers, but have the same identical design geometry as all the earlier versions. They also allow for both OEM pressure fed oiling, or drip down oiling from valve train fed through the push-rods, as most aftermarket blocks required. Only 25 sets of these were made, and NONE of the original buyers, from last we heard, had any interest in selling some of them. Greedy, considering most sales were multiple sets. But that' s the BOSS owners -- not greedy, just passionate.