A coupling member for an ultrasonic instrument assembly includes a body member having a first port at a first end and a second port at a second end opposite the first end, the body member having a lumen or channel extending from the first end to the second end so that the first and the second port communicate with one another. The body member is made of a flexible resilient material and is provided with at least one protrusion (or projection) extending into the lumen or channel. The protrusion is variously insertable into at least one cooperating groove or recess on an outer surface of a tubular member to enable an adjustment in a degree of insertion of the tubular member into the coupling member.
