12mm plywood was reduced on website but should have been marked as second or third quality. Top layer on both sides was rippled on all three boards and one board was badly warped even after being laid flat with other two boards on top. Thickness also varies when laid due to the ripples on the surface. Even when the boards are securely screwed down there are areas which creak as no doubt there are problems with the inner layers whether with the glue or inconsistencies in the layers. Have had ply delivered before with no problem. I am now faced with lifting sanding and filling the boards just to get a level surface which was whole point of using it to overlay the floor boards. Unfortunately this is unlikely to solve the creaking/flexing which is due to problems in the interior of the boards.