About the thickness:
Please read this before you buy, thank you!
1,it is cotton and 0.5mm thick, i used a gauge and checked it against thread i already have that's 0.5mm.i tried it on my sewing machines, singer 201k and a singer 29k patcher and i works fine, it will work with a singer number 19 needle but works best with a singer number 20 or 21 needle
2,you might find it is thinner than the photo shows, thats because when factory rolling them, machine can be adjusted to tight and lose, when its tighter, it will look"thin",but doesnt mean it is not as strong.