So, I bought some of this... http://www.target.com/Comfy-Foam-Ma...mbrowse=0&index=target&rh=k:comfy foam&page=1 to line my B15S cab with. I've read on here, mostly from BillFitzmaurice, that open cell is the way to go. However, the one I bought is not labeled as either. I put in an email to Target, where I bought it, and still no answer. So, how do you tell the difference? And, does it make a difference? I don't want to cut it up and ruin it in case I need to return. Thanks in advance!