If you have the same size needle, use that. If not, it would work better to have a different size needle through the stitches to be bound off than to knit with a different size needle.
Many people use a larger needle to BO regular anyway, I usually use one size up on a 3 NBO. Or I put one set of the sts on a smaller needle and BO with the same size.
Thanks so much. Was always wondering what size to use for third needle. Didn’t know I could switch working stitches to smaller size needle and use same size for BO.
It’s the needle that you work with in the right hand that determines the size of the stitches. So if you’re working in the round or for this type of BO, the left needle can be smaller.