sfp+ cage different sizes in holes

[balamani]

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?

 

[sivamani]

I dont think so the hole is related to EMI.Sizes may be be based on the mechanical strengths.