From USCG website: Developed in a direct response to the need for additional Homeland Security assets in the wake of the September 11th terrorist attacks, the Defender Class boats were procured under an emergency acquisition authority. With a contract for up to 700 standard response boats, the Defender Class acquisition is one of the largest boat buys of its type in the world. The 100 boat Defender A Class (RB-HS) fleet began arriving at units in MAY 2002 and continued through AUG 2003. After several configuration changes, most notably a longer cabin and shock mitigating rear seats, the Defender B Class (RB-S) boats were born. This fleet was first delivered to the field in OCT 2003, and there are currently 357 RB-S boats in operation.
The 457 Defender Class boats currently in operation are assigned to the Coast Guards Maritime Safety and Security Teams (MSST), Maritime Security Response Team (MSRT), Marine Safety Units (MSU), and Small Boat Stations throughout the Coast Guard. With an overall length of 25 feet, two 225 horsepower outboard engines, unique turning radius, and gun mounts boat forward and aft, the Defender Class boats are the ultimate waterborne assets for conducting fast and high speed maneuvering tactics in a small deployable package. This is evidenced in the fact that several Defender Class boats are already in operation by other Homeland Security Department agencies as well as foreign military services for their homeland security missions.