When sourcing treated wood, the most critical factor is the Preservative Retention Level, which determines the wood's resistance to decay and termites. For B2B buyers, you must specify the Use Category (UC) based on the application: UC3B for exterior above-ground (exposed to weather) or UC4A/B for ground contact (posts and landscaping). Additionally, verify the species of timber (e.g., Southern Yellow Pine, Douglas Fir, or Radiata Pine) as each has different structural load-bearing capacities and chemical penetration depths.