Thanks, right after i wrote on the forum I went to the website and saw it is .26. I have been looking at the 1/4 wave and T-line tutorial on the top of the subwoofer and enclosure section of the forum and if my math is right in order for me to be within my measurements of 18x45x33 and have enough cu ft i have to have a tune of 45 hz or so. Can anyone double check me?