Since 1990, I have enjoyed collecting and restoring antique radios and vintage audio.... all items I list will be exactly as described and packed extra well to ensure a safe delivery... buy with confidence! BUYER is responsible for doing their own research to ensure they are buying the correct foam passive radiator for their Velodyne or ESS subwoofer, application, or DIY project. And... for judging whether part is compatible with their speaker's specs ! Once purchased, the order will NOT be canceled for any reason, and there are NO RETURNS! Ask any and all questions BEFORE buying ! For sale is a single 12" foam passive radiator with corrugated cardboard backing. I bought this NEW from Simply Speakers a couple of years ago, but never used it. The part # is PAS-12 at Simply Speakers, and it's made for a few Velodyne and ESS subwoofer models. Buyer should research the various models by going directly to the Simply Speakers website and verifying which brands and models it will support. It has a 2-layer support built into the back of foam... a layer of white plastic with a layer of corrugated cardboard layered on top of the white plastic. The back does NOT have a tethered string adjustable bolt for providing some reverse tension like some of the original Velodyne PR's did. The Velodyne model #s can be confusing... so again, buyer must research and study the model #s to verify this is correct passive radiator for their sub. Following is the same part as this: PAS-12: 12" PASSIVE RADIATOR DISC, 11.625" OD, 2.8 OZ., GRAY (simplyspeakers.com) Ask any and all questions BEFORE buying! Once purchased, the order will NOT be canceled for any reason, and there are NO RETURNS! After buyer has left positive feedback to acknowledge everything OK, I will immediately return the favor.