The Buffer is a one-time $100 cushion built into your funded account. It is not a fee you pay — it is simply $100 of profit that stays in the account once your drawdown locks.
In practice
• Your EOD trailing drawdown follows your balance as it grows
• Once your end-of-day balance reaches the lock threshold, the drawdown locks permanently at starting balance + $100 — for example $50,100 on a 50K account
• From that point your account can never be liquidated below that level, and withdrawals can never bring your balance below it either
That $100 is the buffer: a small cushion that permanently secures your funded account so you can trade freely without fearing normal market fluctuations.
For the full mechanics, thresholds and a day-by-day example, see the article "How does the EOD Trailing Drawdown work?".