Another source of income for HFT firms is that they get paid for providing liquidity by the Electronic Communications Networks (ECNs) and some exchanges. HFT firms play the role of market makers by creating bid-ask spreads, churning mostly low priced, high volume stocks (typical favorites for HFT) many times in a single day. These firms hedge the risk by squaring off the trade and creating a new one. (See: Top Stocks High-Frequency Traders (HFTs) Pick)