In Metal Gear Solid 2: Sons of Liberty, the mass-produced amphibious Metal Gear weapon is Metal Gear RAY.
RAY was designed primarily to counter other Metal Gear units rather than to function as a conventional battlefield tank. Its body is built for amphibious movement, allowing it to operate in water as well as on land. This distinguishes it from Metal Gear REX, the bipedal nuclear-capable prototype featured in the original Metal Gear Solid.
The game presents RAY as a large-scale military platform produced in quantity. Several units appear during the tanker sequence, demonstrating that the technology has moved beyond a single experimental machine. The name is often written in capital letters as RAY, matching the series' stylized naming convention.
Metal Gear RAY should not be confused with Metal Gear REX, Metal Gear ZEKE from Peace Walker, or Metal Gear D from the original Metal Gear 2: Solid Snake. Those machines belong to different games and development periods.