The T4 turret droid was another large multi-legged battle droid from the Colicoid Creation Nest.
The T4 was first built several years before the Invasion of Naboo. The primary function of the droid was to act as a mobile defense platform to protect dignitaries who were visiting hostile worlds. During the invasion, many were redeployed to Theed to enforce the peace and prevent the queen from fleeing. They cost 26940 credits new and were restricted to military usage.