This bracket fits snuggly on 4x4 post which actually measure 3.5" x 3.5".   Construction is 3/16" thick high quality aluminum with full weld coverage over joints.   There are a total of 24 holes, with 8 desiginated to secure the post on all sides.  
 
In addition to the bracket, you get the following
 
24x 2" Stainless Steel Wood Screws
24x Plastic washers
24x Screw caps