To curb excessive volatility, stock exchange BSE today revised the circuit limit for share movement of several firms including four sugar companies. The limits, effective from tomorrow, will ensure stock prices do not go up or down beyond a level during a session. Circuit filter mechanism is used by stock exchanges to keep excessive volatility in check. It is the maximum fluctuation that is allowed during trading, which gets suspended if the permissible limit is hit in either direction. Share price of sugar firms - Uttam Sugar Mills, Ugar Sugar Works, Oudh Sugar Mills, Rajshree Sugars & Chemicals - cannot change by more than 5 per cent in a day, BSE said in a circular. Also Read:\u00a0India markets regulator eases currency derivatives rules The scrips of these sugar firms have been declining in the last few trading sessions after government, last week, imposed 20 per cent customs duty on sugar exports to boost domestic supply and check prices which are ruling high at Rs 40 The exchange has also set an upper limit of 10 per cent for Ashirwad Capital, Future Market Networks and Manaksia Aluminium Company. Besides, it fixed an upper limit of five per cent for Achal Investments and Electrotherm (India). "Trading members of the exchange are hereby informed that the circuit filters has\/have been changed from their existing levels. in the scrips (nine) with effect from June 23, 2016," BSE said.