All depend on how big is the letter,i like to use a 5rl on small letters or 7r for bigger letter
A small needle, size 60/8, is suitable for sewing silk.
In the US, knitting needle sizes are in numbers; crochet hooks use both numbers and letters.
For the most common size that you would be doing it in. Line it with a 3RL, and then do your edges with 5RS. Then do the middle fill with a 15RS. The bigger the letters, the bigger the shade needle size and in some instances, the liner as well.
a 7
You use size B.use a 7 to 9 mag
21 gauge
the pointed side
Butterfly needles
That would all depend on the size and the intricacy of what you are doing.
a hollow needle. Pretty much what you see in hospitals and such. The size depends on whichever one you ask for.
a specially needle is used. the common size for the needle is 14 g, and sometimes they use a 16 g if you don't want the hole to be so large
Sewing by hand, I would use a Sharps Size 8