This coat was made with equal yardage of both KnitPicks yarns held together throughout the project. Because this makes a very dense fabric, the coat weighs about 7 pounds. If that sounds too heavy to you, try using the other recommended yarn, Aspen by GGH Muench.
KnitPicks has discontinued Sierra, but its replacement Cadena has the same fiber content and will work equally well for this project. Wool of the Andes Bulky would also be fine.
It’s VERY important that the selected yarn(s) knit to ball band gauge of 14 sts over 4 inches or 10 cm, BUT for this project, you will use a smaller needle to make a tighter gauge that is really 15 sts over 4 inches or 10 cm. If you choose a yarn which knits to 15 sts over 4 inches or 10 cm on the ball band, this coat will sag out in the rear and that’s the opposite of my intent.