APA rated as underlayment. It could be softwood, might say something like; A/C or B/C, solid core, face sanded, etc. Should state the glues are waterproof and have an exposure-1 rating. Another type and I think a better quality product is maple underlayment. Also, underlayment specific for sheet goods often come in 4'x4' sheets. It might also help if you would tell us which flooring you have.
It would be easier if you could tell us your choices if more than just one.
TILE GUY - retired- TROY, MI - Method & Product suitability consulting.
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