Found Extira.
"What are Extira panels?
• A treated wood composite panel product for non-structural applications for exterior and high moisture interior environments.
• Available in square cut panel dimensions of 49"x 97", 49" x 194" and 25" x 194".
• Available in thicknesses of 1/2", 3/4", 5/8", 1" and 1 1/4" (+ /- 0.005").
• Sanded two sides (S2S) for a smooth, unprimed surface."
Extira Treated Exterior Panel Product Line