The 7336SP, sander polisher comes with a 6-inch counterweight
This should be fine for most situations. PC recommend different counterweights for different pads.
Info-
Counterweights:
The counterweight is a half-moon shaped piece of metal attached to the rotating shaft of the tool, this smoothes out the random orbit action by providing a counter balance to the elliptical orbit of the rotating backing pad. If you change the pad size you must also change the counterweight or suffer unnecessary vibration and possible damage to the tool. Counterweights are attached with two Torx fasteners; size T15.
There are two different counter-weights, which are clearly marked to indicate use with either the 5-inch, or 6-inch backing pad. Therefore with a 6-inch backing pad for polishing you should use the 6-inch, 0.140 oz. counterweight (PN 699933). The vibrations that are generated at higher speeds when using a 5-inch weight and a 6-inch pad are unacceptable for most people for the 5-inch backing pad (or smaller) for polishing you should use the 5-inch, 0.120 oz (PN 874011) counterweight.
JonM