I just finished the back of my calculator. I'm using two strands of Red Heart Worsted. For the first half, I was using Balene needles. Well, I got annoyed because 2 strands of Red Heart on those needles did not slide very well. So I went to the firefly frenzy sale at the local Joanns and got my bamboo needles cheap. Once I changed my needles, the last half of the back went much more smoothly. So here is the back of my calculator, finally finished on my nice, smooth bamboo needles.