STK is a decentralized crypto-currency focused on merchant payments. It is expected to be mainly used at point of sale. It has a partnership with Mastercard. Tokens were distributed in airdrops and through a presale. Tokens are also distributed for claiming bounties. Paying with STK also means that user does not have to pay any transaction fees whatsoever. However, STK tokens are not strictly required to use the Stack App (which is used to make payments). It is expected to launch in Canada in May, 2018 and USA by in q4 2018.