# Tetu.io contracts update 1.6.0

These changes were made since version 1.5.0 and deployed during March-April 2022

Huge changes were made for moving OpenZappeling contracts to a local directory and implementing ControllableV2 for base contracts. These changes were needed for cheaper gas usage on ethereum.

<https://github.com/tetu-io/tetu-contracts/compare/release-1.5.0...release-1.6.0>

## Base contracts

### SlotsLib

A solution for managing contracts slots directly using `byte32`

### TetuProxyControlled

Added additional protection. Now able to set implementation only with Controllable inheritance.

### TetuProxyGov

The same controllable protection.

### Announcer

Adopted for ControllableV2&#x20;

### Bookkeeper

Adopted for ControllableV2. Removed SafeMath.

### Controllable

Replace OZ lib with a local file.

### Controller

Adopted for ControllableV2.

### ForwarderV2

Adopted for ControllableV2. OZ libs moved to local. Implemented temporally shortcut for BAL liquidation through Balancer pool.

### FundKeeper

Adopted for ControllableV2. OZ libs moved to local.

### VaultController

Adopted for ControllableV2. OZ libs moved to local.

### ProxyStrategyBase

Added setBuyBackRatio

### StrategyBase

OZ libs moved to local. Removed SafeMath.

## Strategies

Minor changes for all strategies - moved OZ libs to local, rename some variables, removed SafeMath. Changed buyback ratio for some strategies.

### BalStaking

A new solution for cross-chain farming ve tokens.

### MarketStrategy

A solution for decompound supply profit for market.xyz

### AMB strategy

Moved all contracts to proxies. Fixed some issues.

### MB Strategy

Strategy for farming any assets on QiDAO. A part of AMB logic (without AAVE pipe)