> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rails.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Market Data

> Understanding market specific data

## Market Data Types

The [Get Market Data](/latest/perps/rest-api/get-market-data) endpoint returns a variety of data types for each market. Below is an overview of each type:

* **INDEX**: The current index price for the market. The `value` field holds the price, and `index` specifies the source. See below for index price sources.
* **ASK**: The best ask price (lowest price at which sellers are willing to sell).
* **BID**: The best bid price (highest price buyers are willing to pay).
* **FUNDING**: The final funding rate for the last hour. Used to calculate funding payments for perpetual contracts.
* **NEXT\_FUNDING**: The real-time funding rate for the current hour, providing an estimate of upcoming funding payments.
* **OPEN\_INTEREST**: The total number of outstanding contracts (positions) in the market, indicating market activity and liquidity.
* **24H\_VOLUME**: The total trading volume in the market over the past 24 hours.
* **24H\_COUNT**: The total number of trades executed in the market over the past 24 hours.

### Index Price Sources

Accurate and up-to-date index prices are essential for core services such as funding and unrealized PnL calculations. To ensure reliability and availability, our system uses a multi-source approach for index pricing:

* **Primary Source**\
  [CCIX](https://developers.coindesk.com/documentation/data-streamer/index-cc) — main source of index prices.
* **Backup Source 1**\
  [CCCAGG](https://developers.coindesk.com/documentation/legacy-websockets/AggregateIndex) — used if the primary source becomes unavailable.
* **Backup Source 2**\
  [Hyperliquid](https://hyperliquid.gitbook.io/hyperliquid-docs/for-developers/api/websocket/subscriptions) — secondary fallback to maintain price availability.
* **Backup Source 3**\
  [Kraken](https://docs.kraken.com/api/docs/websocket-v2/ticker/) — last fallback to maintain price availability.

### Funding Rates

The funding rate calculations are detailed in the [Funding Calculation](/latest/perps/formulas/funding) guide.

## Product Specifications

Product specifications for each perpetual contract on the Rails platform are listed below. Most values are consistent across all markets, but `tickSize` is specific to each market.

### Common Specifications

These values apply to all supported markets, which you can retrieve using the [Get Supported Markets](/latest/perps/rest-api/get-supported-markets) endpoint.

| Specification    | Value          |
| ---------------- | -------------- |
| Lot Size         | `0.0000001`    |
| Funding Interval | `Every 1 hour` |
| Min Order Size   | `1 USD`        |
| Max Order Size   | `No limit`     |
| Contract Type    | `Vanilla`      |

### Market-Specific Tick Sizes

| Market   | Tick Size |
| -------- | --------- |
| BTC-USDT | `0.01`    |
| ETH-USDT | `0.01`    |

You can retrieve the latest product specifications using the [Get Product Specifications](/latest/perps/rest-api/get-product-specifications) endpoint.