OKX listed three X-Perps today: SEIUSD, AGLDUSD and CFXUSD, opening at 08:00, 08:15 and 08:30 UTC on 21 September.
X-Perp is OKX’s name for an “Expiry Perp.” The phrase contradicts itself, and the contradiction is the design: it charges funding the way a perpetual does, while carrying a fixed delivery date.
How it differs from a perpetual
From OKX’s own help-centre documentation:
| Standard perpetual | X-Perp (Expiry Perp) | |
|---|---|---|
| Expiry | None | Fixed, 60 months from issuance |
| Funding | Yes, every 8 hours | Yes, every 8 hours (4 hours on some contracts) |
| Anchored to spot | Via funding | Via funding |
| How it ends | Trader closes, or liquidation | Cash settled at expiry |
| Day-to-day feel | — | Identical to a standard perp |
Funding is collected at 00:00, 08:00 and 16:00 UTC, the same clock as Binance. Contract symbols look like BTC-USD_UM_XPERP-040431, where the trailing digits are the expiry. As a contract nears expiry OKX automatically lists a further-dated replacement.
The delivery price is specified tightly: the average of the index price at each second over the final 30 minutes before delivery. The European Economic Area terms instead state that trading terminates at 4:00 PM Hong Kong time and settles on the preceding 30-minute index average.
Three things an arbitrageur has to see first
1. Settlement is not in USDT — it is USDC, USDG or USD
USD-margined X-Perps settle in “USD equivalents.” That lands directly on the problem in our piece on stablecoin depegs: the moment your spot leg, your margin and your funding settlement are not denominated in the same coin, you have acquired an unhedged currency exposure.
This is not our inference — OKX writes it into its own risk disclosure, listing three items: funding accumulating over a long tenor and eroding position value, basis risk arising from the roughly five-year duration, and settlement-currency risk including potential de-pegging of USDC or USDG. An exchange naming that itself carries more weight than any third-party warning.
2. A fixed expiry means a terminal basis convergence
A standard perpetual never expires, so basis is pulled around by funding indefinitely and in principle never has to converge. An X-Perp does: on the expiry date it is cash settled against an index average, so the basis necessarily goes to zero.
Five years is far away, and for most traders it behaves like a perpetual. What it changes is the character of the trade — the two cash flows separated in cash-and-carry versus funding arbitrage both exist here at once: funding collected along the way, and basis collected (or paid) at the end.
3. Over five years, funding is a cumulative term, not a rounding error
This is exactly the first item on OKX’s risk list. At one settlement every eight hours, five years is 5,475 periods. Even at 0.01% each, sitting on the wrong side of that for the full tenor adds up to a number nobody should treat as small change.
Incidentally: OKX’s 8/N divisor is visible in live data today
The ordinary USDT perpetuals on the same underlyings happen to provide a ready-made control group. From OKX’s public endpoint at 08:07 UTC today:
| Contract | Current reading | Interval | Annualised | Cap / floor |
|---|---|---|---|---|
| BTC-USDT-SWAP | 0.010000% | 8 hours | 10.95% | ±0.375% |
| CFX-USDT-SWAP | 0.010000% | 8 hours | 10.95% | ±1% |
| SEI-USDT-SWAP | 0.005000% | 4 hours | 10.95% | ±1% |
| AGLD-USDT-SWAP | 0.005000% | 4 hours | 10.95% | ±1% |
SEI and AGLD are currently on the four-hour schedule and read exactly 0.005%, precisely half of 0.01% — that is the ÷(8/N) factor OKX added to its formula in June. Twice the periods, half the rate, and all four contracts annualise identically at 10.95%.
Sort a scanner by raw reading and SEI and AGLD drop to the bottom; in reality all four are the same. The full mechanism, and why Binance does not divide, is in eight hours to four.
One more same-venue quirk: BTC’s cap is ±0.375% while the other three are ±1%, better than a factor of two apart. Even within one exchange these are not uniform.
What to watch next
- The X-Perps’ actual funding series. The first few periods on a brand-new contract mean little; give it a few dozen before judging how it sits against the same underlying’s USDT perpetual.
- The settlement-currency choice. USDC, USDG or USD — whichever you pick is the de-peg risk you take, and it is not revisable after the fact.
- Do not let “expiry perp” enter your code as a perpetual. A holding-cost model with no expiry field will fail five years from now in the quietest way possible.
One thing that cannot be left out
New contracts, new mechanisms and new venue categories do not raise the ceiling on what this approach earns — it can only collect the funding the market pays. Year to date, Binance BTCUSDT has accumulated 2.103149% over 790 periods, annualising at 2.92%; SOLUSDT is at −0.941791%. Funding turning negative is something this approach genuinely runs into, not an anomaly, and we did not leave the worst years off the table on our track record.
Sources: the listing times for the SEIUSD / AGLDUSD / CFXUSD X-Perps come from the OKX announcement published 2026-09-21; the expiry tenor, funding schedule, delivery-price method and settlement currencies come from OKX’s help centre — the X-Perps guide, what are Expiry Perps and the contract specifications; the three risk-disclosure items (long-tenor funding accumulation, ~5-year basis risk, USDC/USDG de-peg) are quoted from that same guide; the four USDT-perpetual readings, intervals and caps come from OKX’s public endpoint api/v5/public/funding-rate, read at 2026-09-21 08:07 UTC; Binance cumulative funding comes from fapi/v1/fundingRate, 2026-01-01 to 2026-09-21 00:00 UTC, 790 periods. Annualised figures assume the current reading holds unchanged and are comparison values, not expected returns. Past performance does not indicate future results.