Completely CNC-machined from high-grade alloy, immensely strong and light, gold plated. RPM limit has been tested beyond 100,000 RPM. Dynamically balanced. 12 bladed fan design, super quiet and efficient. The fan has built-in safety, the rotor cannot escape the shroud, even if your motor shaft breaks. Virtually immune for foreign object damage, no more expensive replacement of carbon fiber rotors if you suck in a bug. You can use anything from 10 to 16 cells, pick your KV accordingly. 20 pounds of thrust is easily attainable on 12 cells. These are in stock here in New York, ready for immediate shipment. These fans are the latest and greatest, stronger, lighter, and more efficient than anything else out there, for for less money, too. http://www.youtube.com/wa http://www.youtube.com/watch?v=jrHbz9Tg-0E&feature=share&list=UUZx_4VfXqscbvdvsnW4AAlA