Selecting the right core barrel depends heavily on the rock formation hardness and strata stability. For soft to medium-hard formations, a double-tube core barrel is preferred to protect the sample from drilling fluid erosion. For extremely hard or fractured rock, a triple-tube system is recommended to ensure maximum core recovery. You must verify the bit connection type (e.g., NW, HW, or specialized threads) and ensure the inner tube material is high-grade seamless steel to prevent deformation under high pressure.