# Extend the SDK

Besides, users can also customize their own wallet provider in an easier way. The `BTCProvider` class provides default implementations for most Bitcoin interfaces. What users need to do is compare the interfaces of the target wallet with the default implementations of `BTCProvider`. The `CosmosProvider` class provides default implementations for most Cosmos interfaces. What users need to do is compare the interfaces of the target wallet with the default implementations of `CosmosProvider`. 

```javascript
import {
  BTCProvider,
  CosmosProvider,
  TomoChain
} from '@tomo-inc/tomo-wallet-provider'

class XYZWallet extends BTCProvider {
  constructor(chains: TomoChain[]) {
    // @ts-ignore
    const bitcoinNetworkProvider = window?.xyzWallet

    if (!bitcoinNetworkProvider) {
      throw new Error('XYZ Wallet not found')
    }
    super(chains, bitcoinNetworkProvider)
  }

  connectWallet = async (): Promise<this> => {
    const accounts = await this.bitcoinNetworkProvider?.requestAccounts()

    const address = accounts[0]
    const publicKeyHex = await this.getPublicKeyHex()

    if (!address || !publicKeyHex) {
      throw new Error('Could not connect to XYZ Wallet')
    }
    return this
  }
}

class ABCWallet extends CosmosProvider {
  constructor(chains: TomoChain[]) {
    // @ts-ignore
    const cosmosProvider = window?.abcCosmos

    if (!cosmosProvider) {
      throw new Error('ABC Wallet not found')
    }
    super(chains, cosmosProvider)
  }
}
```

Then you can use it in the wallet context provider

```javascript
<TomoContextProvider
  additionalWallets={[
    {
      id: 'xyz',
      name: 'XYZ BTC Wallet',
      chainType: 'bitcoin',
      connectProvider: XYZWallet, // XYZWallet should extends BTCProvider
      type: 'extension',
      img: 'https://your wallet logo.svg'
    }, {
      id: 'abc',
      name: 'ABC Cosmos Wallet',
      chainType: 'cosmos',
      connectProvider: ABCWallet, // ABCWallet should extends CosmosProvider
      type: 'extension',
      img: 'https://your wallet logo.svg'
    },
  ]}
>
</TomoContextProvider>
```