Use whatever yarn you like suitable for the hook size. A larger hook /thicker yarn will give you a larger collar and a smaller hook/thinner yarn will give you a smaller collar so adjust accordingly. For this pattern I used two strands of 4 ply held together. Remember that your collar won’t look exactly like mine as you will likely be using different yarn anyway. This is a great stashbuster as you won’t use a lot of yarn, a 50g ball will suffice.