Great pocketable, waterproof pen
The design of this pen is really quite simple. The cap screws over almost the whole body of the pen and seals with an O ring. The disadvantage is that you have to do a lot of screwing to open the pen, but the advantage is that the inside of the pen should be sealed so it should protect against pocket lint and still work if you fall in a river. More realistically it protects against pocket lint. The cap attaches to the top of the pen just with the friction of another O ring. It's quick to get the cap on and off the end and it does stay on OK, but it feels slightly wobbly and loose which is a shame, but otherwise does form a full size pen that feels nice in the hand, although a bit narrow. You need a flat-head screwdriver to change the refill. I don't see this as a problem - if you really need to change a refill while travelling you'll almost certainly have a flat-head screwdriver on some sort of multitool anyway. It doesn't say on the Heinnie website, but I think it takes Cross 8518 (D, D1) refills, that are just pushed into the threaded piece with the flat-head slot. Actually, this piece screws into the end of the pen with no O ring, so perhaps it wouldn't quite survive prolonged submersion. Overall I really like the look of it and how it really easily fits in my pocket and takes very little space, yet still unpacks to a reasonable size, and unlike many clicky/bolt-action/"tactical" pens, the nib is not just retracted a few millimetres where it can still collect pocket lint but is fully enclosed, so I have a lot of confidence that when I take it out I'm not going to spend the next five minutes scribbling frantically on a scrap of paper trying to get ink to show up.
