As far as I know this is an unused replacement woofer for a Yamaha NS10. It sat uncovered in a fairly dusty environment for a while and the front white part got dirty over time. I've tried a couple of times to wipe it off with a dry paper towel but fear I may just end up doing more harm than good. The rest of the speaker looks to be in excellent condition, and I don't think the dirty cover piece should affect the sound it produces.  Selling at a lower price because of the dirty cover, since most NS10's I've seen have usually been displayed without the main speaker cover screen. Dimensions are just over 7" square, and 3" deep. This listing is for 1 woofer, not a pair.