This is a 4-1/2" Brake Drum with 3 bolt hole patterns
Product Specs: 4.5" OD Machined Drum for Brake Band Use 2.09" ID of Center Hole Works for Hub P/N AZ2561
3 Bolt Hole Patterns: (3) 5/16" bolt holes on a 3-3/4" bolt circle (4) 1/4" bolt holes on a 3-3/4" bolt circle (4) 9/32" bolt holes on 3.225" Bolt Circle