I have two Slimline Pro pen / pencil sets that are my favorite "personal use" sets, and I have been using them for many years. One set is at the desk and the other I use in the shop. I have made many more. The Slimline Pro pencil mechanisms work fine for me, but they are not the best quality I have seen. I have been using similar mechanical pencils all my life, and have learned their quirks and foibles.
They all jam on occasion, and part of owning them is learning how they work, how to fix them when they are not working, and when they are broken (usually when the tiny rubber ring inside gets lost).
The key trick to working with this style of mechanical pencil is learning to recognize when the lead has reached the end and is ready to be replaced. The short lead is about 1/4 inch long at that point. Extend it slightly, pull it out with your fingers, and throw it away. After that, extend the long new lead with multiple clicks until it is ready to use.
If you don't pull out that finished piece of lead and continue to use it instead, the pencil is more likely to jam with a small piece of the short lead stuck in the tip, held by the rubber ring, blocking the new lead, which deflects and jams in the tip. If that happens, you may have to unscrew the tip of the pencil and use a pin or piece of lead to push out the jammed piece in the reverse direction. If you're not careful, you can dislodge, damage, or lose the tiny rubber ring in the tip of the pencil. That renders the pencil useless.
Note: I have not tried any of the EDC Slimline Pro pens or pencils yet. I wonder whether the pencil mechanism is the same as the regular Slimline Pro pencil kits.
I hope this helps.
