What size socket do I need for the plugs on a 94 Civic EX (D16Z6 engine)?

Also, I notice that the service manual notes two different plugs, one
the NGK ZFR5J-11 for "normal" driving, the other the NGK ZFR6J-11 for
"hot climates or continuous high-speed driving". My car is used mostly
for trips, not a lot of local driving. Does primary driving at highway
speeds warrant the 6J plug?

Is another brand recommended? I just discovered sparkplugs.com--pretty
cool. Anyone bought from them? A listing of plugs for my engine:
http://www.sparkplugs.com/results_ap...1&AAIA=1168747
None of these manufacturers means anything to me. It's unlikely that I
need "premium" plugs--not a racer--but if the Champion Premium Gold plug
is any better than the NGK OEM spec, the price is certainly right.

Since the last tune-up on this car was at 97K miles at an unknown date
(now at 118K), and since I don;t know whether the plugs were replaced
then, I'm thinking it might be a good idea to replace them soon.