The Enchanted Infinity Scarf pattern calls for four 4 colors of worsted weight yarn.
When sewn and finished - lying flat - it should measure approximately 28” long and 6” wide.
I used a K hook, but I crochet very tight. I find that my K hook work is comparable to most people’s I hook work. That is why I recommend an I hook.
However, If you know you crochet tight - the you may want to increase your hook size accordingly.