And @DannyP- the rear ones are easy- it's the front (of car) plugs that are hard to get to
Al, rear as in farther away from the spark plug changer. Poopiehead!
Wolfgang: that Hazet tool is nice but it isn't 18mm. 18mm long reach is the standard spark plug used in ALL CB Performance "high-performance" heads. They use 12mm threads instead of the standard VW/Porsche 14mm short reach plugs with 13/16" socket size.
I've found that it is not necessary to grind an 18mm thin-wall six point Craftsman socket, 3/8" drive. It may/probably be necessary to grind the much larger 13/16" socket.