Pilot LHSRF-8C Gel Ink Pen Refill - 0.4 mm - Black

Hacked it successfully into a Fisher Space Pen (the Astronaut variety with a clicker, although refill-wise it doesn't matter). It's a couple of millimeters too short, though, but it doesn't affect writing per se but it's hard to see the tip on paper. Truth be told, I bought this refill in attempts to hack it inside the Coleto multi-pen (due to it being considerably cheaper but virtually identical), but it wasn't possible easily enough. Writing quality and emptying speed are practically the same also.

Just can't get the ink to write smoothly from the LHSRF-8C. I'm on my second refill and I'm having the same issue as with the first, patchy, intermittent ink flow.