Shimano makes seatpost, may come as news to somebody. Well at least they used to, I do not know if they produce seatposts anymore under the Shimano label but the old school posts was robust and relatively nice looking parts.
The black Shimano M730 seatpost has a simple one bolt saddle clamp system that is not known of slipping. Perhaps a bit uncommon in these days of carbon fibre seatposts and frames selling for pathetic sums of 12.000+ dollars on eBay, the Shimano Deore XT seatpost is made of steel.
If you absolutely needs the lightest XT seatpost solution there is you could always replace the steel bolt for a titanium bolt, I guess you could get this seatpost down around the 300 gram mark with some titanium hardware and cunning cutting of the 330 mm original length.
But who am I kidding, if weight is your no 1 priority there is always the M900 XTR seatpost out of Easton aluminium, or as earlier mentioned, todays carbon fibre seatposts, but do not blame me if the mentioned carbon fibre seatpost breaks in half and ends up in your #!&, yes there is a danger of that happening.
So anyways, this is a black Shimano M730 Deore XT seatpost in 26.8 (so it fits vintage Yeti frames such as the FRO and Ultimate) and it is uncut 13 inches long, make that 330 mm if you prefer millimetres. Seatpost is a bit worn in some places but still mostly black with the cool Deore XT logo visible on the top of the post.
Send 16 European dineros + some European dollars for shipping to Tukkholma and the post gets wings ready to fly to your bikes seat tube. SOLD!