Perpetual Contract Product Details

1. Overview

Perpetual contracts are digital asset derivatives launched by SunX, denominated and settled in USDT per contract. Currently, contracts support both long and short positions with multiple leverage options. Perpetual contracts do not have an expiration and use a funding rate mechanism to keep the contract price closely aligned with the spot market. Reasonable mark prices are used to calculate unrealized P&L and liquidation prices to avoid unnecessary liquidations caused by market volatility. The objective of the contract is to replicate spot market conditions under high leverage.

2. Contract Definition

Example of opening a position using BTCUSDT contract:

Q: How is the BTCUSDT contract priced?

A: The underlying price of BTCUSDT is the SunX Index. Both the underlying price and the perpetual contract price are quoted in USDT. All margin and P&L are denominated in USDT.

Traders who expect the BTC/USD index to rise will go long BTCUSDT contracts. Conversely, traders who expect a decline will go short.

Trading example:

If BTC price is 5,000 USDT, Trader Wang buys 100 BTC, equivalent to 100,000 contracts (100 BTC ÷ 0.001 BTC per contract). If the contract price rises to 6,000 USDT, the profit is:

100,000 × 0.001 × (6,000 − 5,000) = 100,000 USDT

3. Fee Rates

Perpetual contract fees:

Taker: 0.04%

Maker: 0.04%

4. Mark Price Calculation

Mark price calculation:

The mark price is calculated using the funding basis rate and price index.

Funding basis rate = Funding rate × (time to next funding / funding interval)

Mark price = Index price × (1 + Funding basis rate)

Accurate calculation of unrealized P&L is essential to avoid unnecessary liquidations. The intrinsic value of the contract is based on the weighted average of major spot markets, forming the price index, which is a key component of the mark price.

Price Index Calculation:

The perpetual contract price index is the weighted average price of major spot exchanges, including Binance, OKEx, Huobi, Bittrex, etc.

Protection measures:

Single source deviation: If any exchange price deviates more than 5% from the median price, its weight is set to zero.

Connection issues: If an exchange does not update within 10 seconds, its weight is zero in the weighted average.

Mark price formula:

Mark price = Median(price1, price2, contract price)

price1 = Index × (1 + Funding rate × hours to next funding / 8)

price2 = Index + 30-minute moving average of (Bid1 + Ask1)/2 − Index

The mark price better reflects intrinsic value, avoiding unnecessary liquidations and market manipulation.

5. Funding Fees

Purpose: Funding fees incentivize price alignment between long and short positions.

SunX does not charge funding fees; they are exchanged between users every 8 hours (UTC+8 00:00, 08:00, 16:00). Positive funding: longs pay shorts. Negative funding: shorts pay longs. Only open positions at funding time incur fees.

Funding fee formula:

Funding fee = Position notional × Funding rate

Funding rate calculation:

Funding rate (F) = Premium index (P) + clamp (Interest rate (I) − Premium index (P), 0.05%, −0.05%)

Premium index (P) = (Max(0, weighted bid − mark price) − Max(0, mark price − weighted ask)) / spot price + fair basis

Interest rate (I) = (Quoted interest rate − Base interest rate) / funding interval

Maximum absolute funding rate: 0.15%