RG-400 M17/128 is a high performance, 50 ohm coax typically used in military and aerospace applications. This is a double shielded coax with (2) silver coated copper braid layers and Teflon dielectric. It is virtually crush proof and excellent in high wear, harsh environments that range from -55C to 200C. The .195 diameter is the same as RG-58AU and is ideal for going through a window or door. The soldered Amphenol connectors provide a finished cable that will provide years of service in the most demanding of conditions. The 12ft 6 inch length is specifically made for CB radio applications. This specific length is 1/2 wavelength taking into account the velocity factor of the coax in use. In this case 69.5%. An exact half wavelength (or whole multiple there of ie. 25, 37.5, 50.0...) mirrors the load impedance. A perfectly tuned antenna (the load) will show a 50 ohm impedance and this is the impedance we want the transceiver to see. Using this length will give better match even when you only needed a lesser amount. All coax assemblies are assembled in house and shipped from Kansas. We take great pride in the quality and workmanship of all of our products. With over 40+ years of experience why buy anywhere else. ABOUT US: Associated Radio Communications has been serving the Amateur Radio Community since our founder returned from WWII in 1945. We pride ourselves on being more than a place to buy equipment. Our experience in helping the amateur radio community over the decades is freely shared. We are more than happy to discuss your particular communications desires, needs, and challenges. Allow us to offer some suggestions to help you plan or improve your station setup to meet most any goals or desires you may have. We have options that allow operation in the most restrictive of environments. Our years of experience allow us to offer the best solution for a given installation. Don't let uncertainty keep you from enjoying your hobby to the fullest. Your success is our success. Yes, we are a real Brick and Mortar, Mom and Pop store and everyone here is a Licensed Ham! (except the dog...)We are located in Overland Park, KS a suburb of Kansas City. Our showroom facility is a focal point for the local amateur radio community. We have information regarding local clubs and events including testing sessions. AUCTION TERMS:1) Customer satisfaction is our number 1 goal. Please contact us before placing a bid if you have any questions or need a clarification. 2) Returns only accepted if items are not as described. RMA required to return an item. 3) If you can't leave a five star positive feed back, please contact us to resolve any issues. 4) Payment is due within 48 hours of auction end. If you cannot make payment within 48 hours contact us before placing a bid.5) We typically ship within 24 hours of receipt of payment and always within 48 hours. We do not ship Saturday, Sunday or holidays.6) We can only ship to your PayPal registered address. 7) Ebay sales for US customers only8) Kansas residents pay sales tax.