One pair (2 each) Limited production 21" dynamic sub woofers. Ideal for Hi-Fi Audiophile Open Baffle sub woofer applications. Matched pair. Cast aluminum frame. Treated non pressed paper cone. 4" voice coil. Vented core. 25 - 200 Hz. usable response. Measured specifications: 8 Ohms nominal. FS: 26.2 Hz. X-max: 7.0 mm peak, X-limit 15 mm peak, SD: 1,706 sq. cm. QTS: 1.54. RE: 6.35 ohms, magnet weight: 100 Oz, calculated efficiency: 93.7 dbw, VAS: 704L 30 lb. net weight. This is a very unique woofer with its combination of area, linear travel, high QTS, operating efficiency and pro quality build. Needless to say, this sub can move a lot of air and with its high QTS requires very little crossover compensation to play down low and loud on a suitable open baffle. Unfortunately they are no longer available. The original supplier, MCM, has been purchased by Newark Electronics and Newark is no longer offered in their product line. If you have been looking for the ultimate in an Open Baffle Woofer, this is the one to have. This is the last pair I have. These are one owner and have very little use. Used for new product development and audio show demonstration by Manzanita Audio Solutions, Inc. Will ship from South West Florida. Will ship in 2 boxes. 75 pounds total shipping weight. $400.00 for the pair, plus shipping.