Thanks for your question. The Curt TruTrack Weight Distribution System w/ Sway Control - 15K system # C17501 you mentioned is a 4 point sway control system. The four points consist of the 2 points where the trunnion bars meet the frame brackets and the other 2 points are near the head where the trunnion bars integrate. There is a spring loaded ball bearing that is another point of friction on each bar giving you the other two friction points. I've attached a photo to assist.
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