Designated as the  AZT 2400 Class, the tugs are true tractors with azimuthing (‘Z-drive’) propulsion units located beneath the forward third of the hull. The Z-drive tractor configuration has somewhat fallen from favour in recent years against the increasingly popular Azimuthing Stern Drive (ASD) configuration. However, for the operator that can accept the inherently deeper draft, this configuration has some attractions, namely slightly higher propulsive efficiency and a more uniform thrust vector pattern around the compass.

In the case of the Neri tugs, the major design challenge was to put the owner's operational requirements, including a twin drum winch and a high standard of accommodation for six crew, into a compact and attractive package that offered good ship handling and escort towing capabilities. Under the design guidance of senior naval architect and project manager Dr. Oscar Lisagor, the owner's objectives have been met with these handsome and powerful little tugs.

The new tugs are intended for both harbour and coastal duty, based in the port of Livorno, and comply with the RINA Class notation;- C+ Hull, C+ Mach, Tug, Fire-Fighting ship 1, Waterspraying, Coastal Area, +SYS-NEQ-1, +AVT-UMS and AUT-PORT, and +Inwatersurvey.

Fratelli Neri and Porto di Livorno, the first of this new AZT 2400 series, have an overall length of 23.8m, a moulded beam of 12.0m, a maximum draft of 5.7m and measure some 300 gross tons. Contained within this compact hull structure are tanks for 120 m3 of fuel and 12 m3 of fresh water.

Two Caterpillar 3516B diesel engines running at 1,600 rpm generate a total of just over 5,700 bhp to drive a pair of Schottel model SRP 1515 propulsion units. Each unit incorporates a 2,600 mm diameter fixed pitch propeller and power is transmitted via a Cardan shaft system. This combination delivers a bollard pull of 69 tons ahead, 65 tons astern, and a free running speed in excess of 12 knots.

Electrical power is provided by a trio of Caterpillar C.4.4 alternators, each rated 86 kW, 50Hz at 1,500 rpm.

The main towing winch supplied by Kraaijeveld is hydraulically powered and has two large independently driven drums. Each drum is aligned with its own stainless steel lined fairlead.

The tugs have a full Fi-Fi 1 rating in accordance with Class notation requirements. Two remotely controlled monitors are mounted at bridge deck level and supplied by fire pumps coupled to the front end of the main engines. The pumps are driven through Kumera step-up gearboxes that also drive the main hydraulic pumps for the deck machinery.

The tugs are fitted out for a crew of six persons, in a necessarily ‘cosy’ but modern and well- equipped fashion. The entire deckhouse is resiliently mounted to provide a low noise level in accordance with Italian registry regulations.