This allowed the RoC to accumulate experiences in the overhauling, welding, parts manufacturing, vehicle assembly, and testing of the M113 APC.

The Wan Cheng 2 is an attempt to create a light tank by moving the engine to the rear and lowering the front half of the hull to accommodate a M24 turret while keeping the vehicle from being top-heavy.

[3] The Wan Cheng program provided a solid foundation for the design, manufacture and development of the CM-21 armored vehicle.

It is largely the same as the basic M113 and inherits the same engine and transmission from the source design, but the welded aluminum alloy hull armor is further augmented with spaced armour at the front and the sides, the cavity within the spaced armor being filled with polyurethane to absorb the energy of incoming projectiles.

The engine's intake has been modified to take air from the inside of the vehicle, rather than using exhausted gas, which reduces the crew's performance in combat.

The side armor is also replaced with a net armour to protect the vehicle from anti tank weapons with shaped charges.

The CM-25 has a modified passenger compartment to store TOW missiles, and has replaced the quad-mounted smoke grenade launcher with triple mounted ones.

The spaced armor of CM-25 is filled with polystyrene to increase buoyancy for the Marine Corps' amphibious operations.