TWSBI Diamond 580AL Silver Fountain Pen nib F;

A quick no brainer guide in choosing nib sizes in an overly complicated fountain pen world: If you write small, go with an EF
 For the normal writer, F is the most popular
 If you tend to lean on a bigger font, M will be perfect 
B is for statements!! Sign a check in B, write a header in B, do some coloring/shading in B
 Stub nibs are italic in writing style (have a special card or invitation to write?)