I always travel with a towel, I use my towel for shade, for screening myself to get changed, as an extra layer over my sleeping bag when I’m cold, as a ground mat when using my 3/4 length bedroll and if it’s clean enough, to dry myself….
“A towel, is about the most massively useful thing an interstellar hitchhiker can have. Partly it has great practical value. You can wrap it around you for warmth as you bound across the cold moons of Jaglan Beta; you can lie on it on the brilliant marble-sanded beaches of Santraginus V, inhaling the heady sea vapors; you can sleep under it beneath the stars which shine so redly on the desert world of Kakrafoon; use it to sail a miniraft down the slow heavy River Moth; wet it for use in hand-to-hand-combat; wrap it round your head to ward off noxious fumes or avoid the gaze of the Ravenous Bugblatter Beast of Traal; you can wave your towel in emergencies as a distress signal, and of course dry yourself off with it if it still seems to be clean enough.”
But it’s not Ultra light, infact my usual towel turned out to be a whopping 269g so for trekking I picked up a microlyte towel in the sales which weighs in at 47g (when removed from the 15g carry case)
That is a saving of 222g