Reflector Finance issues RAI - Decentralised non-pegged stable asset. Users can provide crypto collateral to issue reflex indexes. Reflex indexes are stable assets that are not pegged to anything, very similar to how the US Dollar is not pegged and it is still considered stable. The system behind RAI only cares about the market price getting as close as possible to the redemption price. The redemption price will almost always float (thus, it won’t be pegged) in order to compel system participants to bring the market price toward it.
To put it simply users can leverage their ETH by borrowing $RAI if you expect the ETH price to go up, Which can create sell pressure on RAI bringing prices down and resulting in lower costs of borrowing.
FLX is RAI System Ungovernance Token and Lender of last resort. Flex protocol is Well documented with high quality code and a strong dev team. FLX token is not trading and can be mined by providing Liquidity to RAI Protocol.