This kind of armor is usually found in stacks of 1d8+2. You need only use a bonus action to don or doff it. As a reaction to an attack that would cause you to go below half your hit point maximum(regardless of your current health) you can take no damage from that attack. After being used in this way, the armor shatters into pieces and is destroyed. Otherwise, it functions as a normal breasplate.

This armor consists of a fitted metal chest piece worn with supple leather. Although it leaves the legs and arms relatively unprotected, this armor provides good protection for the wearer's vital organs while leaving the wearer relatively unencumbered.