These fingerless mitts are easily modified by changing the hook size. I used a 4.00mm hook for mine, but a 4.5mm hook would give it a bit more easement. The mitts will stretch over time.

There is no ‘right’ yarn to use. I made 2 pairs of mitts out of three balls of Dollar Tree (50g) knitting worsted. I tend to use whatever yarn I have on hand, and most of it is some form of #4 weight yarn.