Italian brand FRM is no stranger to extremely lightweight parts, but their secrets to shaving grams goes far beyond just using more (or less) carbon and titanium. At some point, the designs have to be rethought in order to go beyond what most reasonable folks would consider normal. Case in point is their ingenious OBI1 dropper seatpost, which flips the orientation to drop significant weight.
But putting the outer tube on the top, they minimize the extra material while also keeping the active post diameter much larger than on standard dropper seat tubes. The mechanical internals and release mechanism sit inside the main seat tube, with only the mast sliding up and down over the main tube.
The limitation is that an external mast can only slide so far before hitting something, so travel is capped at 60mm. And there’s a 90kg (198lb) rider weight limit. Considering it’s aimed exclusively at XC racers, and gravel and monstercross riders, that seems acceptable. Claimed weight is 295g for the post, plus cable and remote weight. It’s available in 27.2, 30.9 and 31.6 diameters, all at 400mm total length. Retail is €590.