While an 8 in-lb torque wrench is best, this thumb driver will help keep your SMA connections tight during radio operations.  Especially if you have a connection that is being moved a lot, like a connection to a handi-talki.  The thumb driver has been sized to fit over the flats of a standard SMA plug (nut) so it can easily rotate in any situation or move between barrel connections, especially if both nuts are already tightened.