Countermeasures are one-time use equipable items in Hawken. They must be equipped in the equipment section of your mech and must be activated in the standby screen while selecting your mech for match. When the time is appropriate, the countermeasure will automatically be activated, using up a countermeasure charge. After this the countermeasure will not be available till the next death.
Instead of purchasing specific countermeasures, you buy countermeasure charges, which are shared across all mechs. You then equip specific countermeasures for your mechs. The prices are as follows:
1 Charge - 107
10 Charge - 1068
50 Charge - 5180
100 Charge - 10146