There are a few reviews of the regular, and kingsized Bulkfillers, but to my knowledge there is little reference to the slimline on the English speaking boards. So below I submit my opinions on this writing instrument:
When I first heard that there was a new filling system on the block I was immediately intrigued. The bulkfiller mechanism is reminiscent of the telescoping piston mechanism used in vintage Montblancs.
For those that don’t know: The telescoping piston mechanism differs from your modern piston fillers in that the volume of all the moving parts is reduced by having the stroke recess into itself, aka telescoping. A smaller footprint in the barrel results in a higher ink capacity. A true mechanical marvel. These pistons were typically made out of brass giving those pens a very nice heft. Fountainbel has a very nice schematic of this ingenious filler here.
In fact, I think that comparison is quite appropriate. In my humble opinion the telescoping piston system was the best engineered ink intake system up until now. Conid’s website has a nice video demonstrating how their filling mechanism works. It is really simple to use. The new Bulkfiller just slightly edges out in front due to the ink shut off valve and double reservoir. My apologies for my bluntness, but I am trying to give really high praise here.
The specific model I have is the Slimline. I have never been a fan of huge pens. Posted the Slimline is the perfect size for me. The size is almost identical to a vintage Montblanc 142 with the previously mentioned brass telescoping piston filler. Shown below my gray-green striated celluloid 142. The build quality is top notch. The Delrin plastic truly is a new tactile sensation. Silky is a great way to describe it. The titanium trim is titanium...light and strong. I’m a metallurgist so I’m not as impressed perhaps Titanium is not the most scratch resistant material and difficult to work with. Anodized Aluminum would has a nice matt finish that is quite scratch resistant, but not nearly as sexy sounding.
Posting of the cap feels extremely stable and I have no fears of the cap falling off. They sit on the double O-rings on the filler knob. Functional and aesthetically pleasing. I prefer a little more weight toward the front of the pen when posted so all the metal trim throws it off just slightly. But here I am being nitpicky. Anodized tantalum threads in the section would be something that catches my attention and add some quality heft to the front end, but that single modification would probably increase the price of the pen by 50-75%....
The laser etchings of the cap bands and are simple, understated and elegant - although not particularly deep. Production volume of these pens is small and they are made completely from machined parts. I believe that the titanium clip is machined using a wire EDM (electric discharge machining). If you look closely enough you can see the signs of machining on the cap and clip. Not defects, but signs that these are indeed turned individually.
You might have noticed that my Slimline does not have a Bock nib. I ordered the pen with both B steel and F titanium plumes. Both nibs wrote beautifully and I would highly recommend both. However like most modern nibs, they lacked the character of vintage gold. Luckily I have a Waterman Ideal no.5 nib that was easily outfitted to the pen (some modification of the feed was required). And now it writes a beautiful XF flex line.
The Bock feed does an excellent job keeping the flex nib happy with wet modern inks (iroshizuku inks notably). However the very dry iron gall inks I tend to use (R&K Scabiosa) leave me with railroads on occasion. At the end of the day, I do not actually flex very much so it is not an issue. This set-up does an excellent job!
The Slimline is supposed to be a "smaller pen" but besides being ~1cm shorter than a Lamy 2000 or Pilot Vanishing point, it is still a great size.
Overall the Conid Slimline Bulkfiller is a fantastic pen: engineered to perfection, completely self-serviceable. Industrial is a good way to describe it. To me at least, pens are tools so I for one can’t imagine higher praise.