The Eyelet Button Hole tends to be my go-to button hole. It’s tiny and unobtrusive so it’s nice for cardigans that might be worn unbuttoned. It’s simple to work (k2tog + yo) and can be accomplished in one row. It makes a nice small button hole so it’s handy when working with a larger gauge and it doesn’t tend to stretch very much over time. It’s my favorite.
It’s by no means perfect, though. It’s not especially strong because a lot of stress is placed on the single strand of yarn from the yo. I only ever use it with sturdy yarn and I generally only use it with worsted weight or heavier yarn. I would never ever ever ever use it with single ply yarn. I just wouldn’t trust the button hole to hold.
Is there anything else that you’d like to know about button holes for these posts? I don’t think I can accurately give the size of them or anything as specific as I did with the stretchy BOs & COs.