what are the most common letters that people struggle with when stuttering?

what are the most common letters that people struggle with when stuttering? Do people stutter on the same set of letters or is it more personal to each person? I used to stutter and “m” “s” “j” and “L” were the hardest I remember. Is this normally what other stutterers had trouble with. For me, any consonant sound was risking being stuttered if it was at the first word of the sentence. Vowels were easy at any time. Is this generally the same with everyone else, as in when people have extreme stutters, then they have more consonants that are hard to say? But when its less severe, there are only a few consonants well known for being hard to say when someone has a stutter?