When evaluating a jaw crusher, the most critical factor is the Feed Opening Size (Gape x Width), which determines the maximum size of the rock the machine can accept. You must also verify the Closed Side Setting (CSS) range, as this dictates the final product size and throughput capacity. For heavy-duty mining or construction, prioritize units with high-manganese steel (Mn13Cr2 or Mn18Cr2) jaw plates to ensure wear resistance and longevity. Additionally, check the Eccentric Shaft material, which should ideally be 42CrMo alloy steel for maximum fatigue resistance under high-stress loads.