To unscrew nib and feed from the front section of a 144, a special tool is required that engages in the feed and turns it without damage. Since the front sections (sections) are mechanically not compatible between Slip Cap black and Twist Cap Solitaire versions, a swap is only possible via nib + feed together, not via the entire front section. Without experience and matching tool, own attempts are advised against, since the plastic parts can quickly break or scratch.