The O'shea 10'2 Inflatable Paddle board HD (Heavy duty) is a dual ply constructed paddle board.  As with the whole O'shea range they use a Mirosol drop stitch fabric, this is the best money can buy and the benefits are; greater stiffness, lower operating pressure -15 psi (many brands need 20psi to achieve the same rigidity) , higher tensile strength of the connecting strands.  This produces a stiff board  at a lower pressure, thus putting less stress on the seams - always a weak point for poorer built inflatable boards.  The dual ply construction achieves a Russian doll concept - a board within a board, making the HD our choice for school and hire use.  The boards copes easily with the unforgiving demands from hire and school use/abuse - always a good test for any product.  If it lasts in the commercial environment the product is great and the O'shea HD Inflatable SUP boards certainly do that!!!