# Overview

See how Zipper moves supported assets between external chains and your Polyester account.

**Zipper** is Polyester's decentralized asset-wrapping protocol, built specifically to bring external liquidity onto Polyester Chain. It powers deposits and withdrawals by validating each transfer, representing the asset on Polyester Chain, and crediting the matching unified balance to your account.

Zipper is designed to support native assets from virtually any blockchain architecture. The resulting assets are issued on Polyester Chain for use across the Polyester Exchange, lending markets, and the broader Polyester ecosystem.

This lets you deposit through one supported chain and later withdraw through another compatible chain without managing wrapped tokens or an external bridge yourself.

## How deposits work

1. You send a supported asset to the deposit address assigned to your account for the selected chain.
2. Zipper waits for the external transfer to reach the required confirmations.
3. Zipper validators independently confirm the chain, asset, amount, and receiving account through a two-thirds (2/3) quorum.
4. Polyester creates the route-specific **Zipped Asset**, or **zAsset**, on Polyester Chain.
5. Your account receives the matching **Unified Asset**, or **uAsset**, in Funding or Trading based on your deposit settings.

Each Main Account and Subaccount has its own deposit addresses, so Zipper can credit the correct account automatically.

## How withdrawals work

1. You choose a Unified Asset, destination chain, amount, and address.
2. Zipper selects the exact supported route and reserves the amount and route fee.
3. Validators approve the request, and the Cubist-protected vault prepares the external transaction.
4. The route-specific Zipped Asset is locked before the external asset leaves the vault.
5. The custody system releases the external asset and Zipper follows the destination transaction to finality. After finality, Zipper burns the locked Zipped Asset.

You can withdraw an available balance from Funding or Trading through the supported withdrawal flow.

## Zipped Assets and Unified Assets

A **Zipped Asset** identifies one exact source chain and asset on Polyester Chain. Bitcoin becomes Zipped Bitcoin, or zBTC. USDT deposited from Ethereum, Solana, and Base creates three separate Polyester Chain ERC-20 Zipped Assets, each backed one-to-one by the exact USDT held on its originating chain.

A **Unified Asset** brings compatible Zipped Assets together as one account-facing balance. This is the asset you see in Funding, transfer to Trading, and use across Polyester.

Only routes that Polyester explicitly connects share a Unified Asset. Matching ticker symbols alone do not make two assets equivalent.

## Routes, fees, and availability

Every route defines its chain, asset contract, minimum amount, confirmation requirement, custody path, and fee. The configured route fee is an absolute amount in the asset being deposited or withdrawn, not a percentage.

The same base route fee applies to deposits and withdrawals on that route. Fees are calculated to cover the source chain's gas costs while keeping the amount charged to you as low as possible. They can change as chain costs and asset values change.

Availability can differ by chain because every supported asset and source chain has its own external supply.

## Explore Zipper

- **[Asset Lifecycle](https://testnet.polyester.com/docs/user-docs/zipper/asset-lifecycle)** explains the complete deposit and withdrawal journey.
- **[Vaults](https://testnet.polyester.com/docs/user-docs/zipper/vaults)** explains deposit addresses, external custody, source-chain supply, and withdrawal liquidity.
- **[Validators](https://testnet.polyester.com/docs/user-docs/zipper/validators)** explains independent request checks, quorum approval, and progressive decentralization.
- **[Security](https://testnet.polyester.com/docs/user-docs/zipper/security)** explains validator quorum, security screening for OFAC sanctions and transaction risk, Cubist TEE vaults, finality, and duplicate prevention.

> **The complete route defines the asset**
>
> Zipper uses the selected chain and exact asset contract, not only the ticker symbol. Native, wrapped, and externally bridged versions remain separate unless Polyester explicitly supports and maps them.

## FAQ

### What is a Zipped Asset?

A Zipped Asset, or zAsset, represents an asset from a specific source blockchain on Polyester Chain. It is backed one-to-one by the original asset held on that source chain. For example, USDT deposited from Ethereum and USDT deposited from Solana create separate Zipped Assets, each tied to its original network. [Learn about Zipper.](https://testnet.polyester.com/docs/user-docs/zipper/overview)