ProComm JBC986 Heavy-Duty 3-Inch Ball-Mount with Barrel Spring Heavy duty ball mount with potbelly spring Works with any antenna with 3/8" bolt Ball will swivel to allow you to mount the antenna on a vertical, horizontal or angled (flat) surface and still have the antenna straight up and down Attached to the mounting screws are two lug coax connections 2-3/4" from mount surface to ball edge, 3/4" from inside of mount surface to bolt edge, 3-1/2" mounting plate diameter, 4" spring height