Better late than never.

Three days after the implosion of an exchange-traded note betting on low volatility, Fidelity Investments said it had moved to protect investors from these products.

The fund giant is halting customer purchases of three volatility-focused ETFs, Robert Beauregard, a company spokesman, said in an email. They are: ProShares Short VIX Short-Term Futures (SVXY), VelocityShares Daily Inverse VIX Short-Term ETN (XIV), and the VelocityShares Daily Inverse VIX Medium Term ETN (ZIV).

The investor purchase ban of the three ETFs began on Feb. 6. Bloomberg News

The ban started Feb. 6, Beauregard said. The firm didn’t issue the news publicly until Friday. “We are allowing customers to sell out of existing positions,” Beauregard said.

Representatives for TD Ameritrade Holding and Charles Schwab said Friday that customers can still trade SVXY. Ameritrade, however, is holding a 100% margin requirement for those purchases, spokeswoman Kim Hillyer said.

Brokerage firms including E-Trade have moved to protect customers as global markets have plunged and volatility has surged. The fallout from the implosion of a vast array of arcane bets against stock market volatility mounted this week. Credit Suisse moved to liquidate one investment product and more than a dozen others were halted after their values sunk toward zero.

SVXY is down 91% since last Friday, XIV plunged 96% and ZIV fell 27%.

Fidelity said customers who want to buy funds that borrow money to increase their returns must sign an agreement that lays out the risks of the products and acknowledge that they have a “most aggressive” risk tolerance.

Bloomberg News