The access fee caps help to ensure that market participants have fair access to the best displayed prices, the SEC said in a fact sheet.

The price increments at which thousands of stocks and ETFs are quoted look set for an overhaul Wednesday, when the US Securities and Exchange Commission votes on final rules to reduce them to less than 1 cent.

Wall Street's top regulator on Wednesday unanimously voted to allow stock exchanges to price many shares in increments of half a penny, rather than the current minimum size of 1 cent, aiming to promote more competitive pricing and reduce investor costs on the $55 trillion U.