Overview:
Here is the first of some cowls I’ve recently made for cooler weather coming & for teaching. They are simple tubes worked in Tunisian Simple Stitch (TSS) in the round using a double-ended (DE) hook.

Size:
These cowls are between 21” and 25” around, and between 8.5” and 12” tall. In general, the heavier the yarn, the larger the circumference and greater the height.
e.g. This one in 4ply Not just socks yarn with 4.5mm hook is 21” x 8.5”. (compare #3 in 10ply Florentine yarn with 7.0mm hook measures 25” x 12”)

Video: Tuula Maaria has a great video on working TSS with a DE hook in the round https://www.youtube.com/watch?v=9H2DduPyEHg&list=PLSG...

Fabric: Use a DE hook large enough that your work drapes. You’ll probably need to go up 1-2mm from the hook recommended for the yarn.

Yarn/Hook combinations:
250m / 60g 4ply Not just socks yarn, 4.5mm DE hook. ch 120.
150m / 50g 8ply Crilly brown multi yarn, 6.5mm DE hook. ch 70.
150m / 100g 10ply, Florentine green multi yarn, 7.0mm DE hook. ch 56.

Curl:
This stitch tends to curl/roll which is part of the design here and nothing to worry about. This will happen more if you’re working lighter yarn with a hook only a little larger than that recommended for the yarn. If your working with a heavier yarn & creating a very soft fabric by using a larger hook, your work will curl less and you might want to work your 1st FP into the back humps of the chain for a neater edge as it’ll be exposed.
e.g. 4ply socks yarn, 4.5mm hook has lots of curl, 1st FP in top loops
e.g. 8ply acrylic yarn, 6.5mm hook has no curl, 1st FP in back bumps

Instructions:
Starting chain needs to be at least 22” / 56cm long for a comfy tube that fits easily over your head (but see note on size above). For this sock yarn with a 4.5mm hook I chained 120.
Slst join to 1st chain to form ring.
Begin 1st FP by picking up a loop in top of each chain as far as you can.
Turn & slide loops to other end of DE hook.
Slst join 2nd ball of same yarn (or another yarn/colour if you choose) & work RP until a minimum of 3 loops remain on hook.
Turn & continue working TSS in spiral rounds with DE hook until work measures around 9” / 23cm (or desired height - see size note).
Work a slst bind off round. You may choose to use a smaller hook for your bind off for a firmer, neater edge. e.g. I used 5mm standard hook for the 8ply Crilly cowl which had been worked with a 6.5mm hook.