I was a fan of the Sierra, but have had a few problems with a couple recently.
In one top half of the turning mechanism came and Is stuck in tube on another I tried to knock out the clip end and it came apart in three pieces with the brass insert still firmly stuck in the brass tube. I can get an replacement tube but not the clip end so I am 2 pens down and can't fix......
So looking around for a similar pen with different type of mechanism.....