Electrosurgical instrument which reduces collateral damage to adjacent tissue

An electrode assembly for use with an electrosurgical instrument having opposing end effectors and a handle for effecting movement of the end effectors relative to one another. The electrode assembly comprises a housing having at least one portion which is removably engageable with at least one portion of the instrument and a pair of electrodes each having an electrically conductive sealing surface and an insulating substrate. The electrodes are removably engageable with the end effectors of the instrument such that the electrodes reside in opposing relation relative to one another. The dimensions of the insulating substrate are different from the dimensions of the electrically conductive sealing surface to reduce thermal spread to adjacent tissue structures.