This has the expander plug. The top cap is also the adjustment mechanism, it is internally threaded and screws onto the expander. I can tighten the cap and get the headset tight enough, but not too tight. Usually I can slightly over tighten a headset, then back off to the correct tightness. Any explanation as to the limited amount of adjustment with this headset? BTW, I checked and nothing has bottomed out, not the stem/steerer or the cap/expander. Thanks for any insight.