These plastic syringes are typically used to dispense electrolyte gels or cremes (but not pastes) onto an electrode surface or into small openings in electrode caps.  Luer-Lok type syringes use a special threaded interface to permit quick and reliable attachment of a dispensing tip (blunt needle), whereas the Monoject type incorporate a permanently attached curved plastic tip with a graduated diameter.  The Monoject type of syringe tends to be more welcome when working with children or other participants who are squeamish about needles.