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I'm one of those people who will fit any refill to any pen, if it's physically possible to. So when I bought a vintage Write Bros retractable and the refill which was full just wouldn't work I had to sort something out myself. I got a Lubriglide refill and made an adapter using a section of gel refill stem and in the centre of that a section of ballpoint stem which when cut to the right length enables the pen to work as normal. How it fits together is shown in the pictures, and the way it does means it is always adjusted correctly.