The ADEN Mk 5 became the basis for the planned ADEN 25, which was to be a somewhat larger weapon (length: 90 inches (2,290 mm), weight: 203 pounds (92.1 kg)) firing the new range of NATO25 mm ammunition (as in the American GAU-12 Equalizer) at a much higher muzzle velocity of 3,445 feet per second (1,050 m/s). The lighter ammunition was also to produce a higher rate of fire, 1,650 to 1,850 rounds per minute. Unfortunately, severe development problems plagued the ADEN 25, which proved unable to meet its design weight target.[4] It was finally cancelled in 1999. As a result, RAF Harrier GR.7 and GR.9 aircraft did not carry cannon, no attempt apparently having been made to retrofit the older ADEN 30 mm pods. Fleet Air ArmSea Harriers retained the 30 mm weapon until their retirement in 2006.