Actuator Arrangement for use in a Fuel Injector

The present invention relates an actuator arrangement for use in a fuel injector, comprising: a piezoelectric actuator having a body section, said body section having a first end piece and a second end piece; a sleeve which enshrouds at least part of the body section of the actuator; and at least one constrictive member, disposed externally with respect to the sleeve wherein the constrictive member applies a constrictive force to the sleeve to maintain a seal between the sleeve and the underlying body section of the actuator. The underlying body section comprises an alternation of smooth sections and rough sections; said rough sections comprising superficial markings.