Flex weapons are the weapons that are available in the final stage of Epic Fragment event. They can only be obtained once per account and cannot be traded.
- Main article: Psychic Sizer
This is a customized weapon of Psychic Harmonium, a sonic weapon produced by Gunsmith. It can use sonic shot attack using sonic energy and sonic pulse, which is an all-round attack, and combines special commands. By doing so, new and powerful potentials can be used.
- Main article: Astra
A weapon specialized for hunting zombies produced by the Aegis Lab. After the projectile flies through a certain distance, it returns to the user again. At this time, if the Astra is still out when it returned, the projectile is recovered; otherwise, it will be destroyed. Projectiles can be fired one more time before being retrieved. Scoring a headshot deals prolonged damage and also strikes nearby enemies.
- Main article: Thunder Force
A weapon made of a lightweight alloy created by a private sector directed-energy lab that researches lasers. Equipped with a feature that automatically attacks enemies with infinite energy bolts.
- Main article: Inferno Cannon
A shotgun that rapidly fires 45 rounds of 12 gauge shotgun ammo. Its special feature, Infernal Flame, allows it to shoot fireballs.
- Main article: Scorching Auto-Shotgun
A customized version of the Hunter-Killer shotgun, a 30-round 12 Gauge shotgun developed by Kronos. The Hunter-Killer Module allows you to use Tactical Scanning in full auto mode, marking zombies after landing enough hits on them.
- Scorching Auto-Shotgun is the first Flex weapon, also the only flex weapon that isn't transcendent grade (is unique grade instead) and the only unique grade that has hit-markers feature found in the transcendence series.
- They were originally available in the Epic FLEX Box until the release of Thunder Force, which starting with that weapon, it has to be bought from the corresponding Epic Fragment store along with it's corresponding Epic during the sale.
- These weapons are not available in VVIP and Hero store in Counter-Strike Nexon: Studio with the exception of Thunder Force and Psychic Sizer, however, they are available in CSO Korea's VVIP and Hero stores.
- Psychic Sizer is the first Flex weapon to be based in a limited transcendence weapon instead of a Lunar New Year weapon
- Most Flex weapons were based in older Lunar New Year weapons.