In 1944 and 1945, 500 T66 multiple rocket launchers were manufactured. They saw service in World War II and the Korean War. The self-contained system had built-in azimuth and elevation adjustments. It was light, easy to maneuver, and could put out a devastating volume of fire in a short time. These features were needed because the back-blast and rocket smoke produced during firing instantly revealed the launcher's position.

8x3 4.5 Inch Rocket Launcher, T66

The T66 and T66E2 multiple rocket launchers were designed to fire 4.5-inch diameter rockets. Produced near the end of World War II, these systems were deployed in limited quantities before the war ended. Multiple revisions to this system were produced, with the 24-tube version named the Honeycomb. There were 15- and 60-tube versions as well, with the largest being called the Hornet's Nest.

The T66 used two different types of rockets during its service life: The M8 and the M16. The M8 was the first rocket used in the T66, with service during World War II. The M16 entered service just two months before the war ended, and all T66 tubes were fitted for this rocket by the onset of the Korean War. Each rocket was unguided and had a solid fuel supply, and weighed around 43 lbs.

The T66 variant applied to the first 206 weapon systems, while the T66E2 variant applied to the next 294. Several improvements were made on the T66E2, including an improved elevating mechanism, a blackout lighting system, a new lunette, a redesigned utility box to house the blackout lighting system, a redesigned conductor cable that was about 50 feet in length, redesigned contact fingers and holding assembly, and a different sight.

The progression of missile and field artillery technology after the Korean War made the Honeycomb and other rocket launchers obsolete by 1954.