- (a) Forty-five day tolerance provision. An index that is a narrow-based security index that becomes a broad-based security index for no more than 45 business days over 3 consecutive calendar months shall be a narrow-based security index.
- (b) Transition period for indexes that cease being narrow-based security indexes for more than forty-five days. An index that is a narrow-based security index that becomes a broad-based security index for more than 45 business days over 3 consecutive calendar months shall continue to be a narrow-based security index for the following 3 calendar months.
- (c) Trading in months with open interest following transition period. After the transition period provided for in paragraph (b) of this section ends, a national securities exchange may continue to trade only in those months in the security futures product that had open interest on the date the transition period ended.
- (d) Definition of calendar month. Calendar month means, with respect to a particular day, the period of time beginning on a calendar date and ending during another month on a day prior to such date.