Hi,

PCB layout of any SFP+ cage (single port or Multiple ports) shows two or three different hole sizes (Datum A,B and C Holes ).

What is the importance of the holes ? Do they help in reducing EMI?

Why are different sizes of holes to be provided?

 

Got a link to the thing you have a question about?

Generally the mounting holes are to catch various pegs made in the EMI shield, most to make a ground connections, a few just for alignment.