Encased in a hermetically sealed canister, the 116 wedges are made from felt and saturated with 0.6 ounces of white phosphorus each¹⁰. When the projectile bursts, the wedges are exposed to the air and begin to burn emitting a thick white smoke as they fall to the ground. The smoke lasts for 5-10 minutes unless oxygen is withdrawn by flooding or smothering the wedges.

Charred wedges retain up to 15% of their white phosphorus content and can re-ignite if the felt is crushed or re-exposed to the atmosphere¹¹. Dormant wedges can re-ignite several weeks after having been deployed. The wedges burn at up to 1500 degrees Fahrenheit and can set fire to objects they come into contact with¹². When wedges come into direct contact with people, they can burn through clothing and continue burning through skin, right down to the bone causing both thermal and chemical injuries.

The incendiary effect of the burning white phosphorus wedges accompanies any employment of the M825 WP, regardless of its intended military purpose.