What material is this core bed made of?

This patented Pilates reformer features a main frame crafted from select oak wood, known for its high density and stable grain, providing excellent resistance to compression and deformation, ensuring stability and reliability even with frequent, long-term use. The bed frame structure is reinforced, with key stress points utilizing metal connectors for enhanced overall load-bearing capacity and safety. The sliding rails are made of wear-resistant alloy material, processed with precision engineering for smooth, quiet, and durable operation. The spring system uses high-strength steel, providing stable and consistent rebound with clearly defined resistance levels to meet various training intensity needs. The mattress uses high-density rebound foam, covered with wear-resistant, non-slip leather, offering a delicate touch, easy cleaning, and resistance to cracking. All materials meet fitness equipment standards, balancing durability and comfort, making it suitable for long-term use in Pilates studios, gyms, and professional studios.