Fidelity Investments is halting investor purchases of three volatility-focused exchange traded funds to protect customers from outsized risk.

The products are: ProShares Short VIX Short-Term Futures (UVXY.K), VelocityShares Daily Inverse VIX Short-Term ETN (XIV.OQ), and the VelocityShares Daily Inverse VIX Medium Term ETN (ZIV.OQ).

The ban started Feb. 6, said Robert Beauregard, a company spokesman.

“We are allowing customers to sell out of existing positions, but no one can buy into them,” he said.

The Financial Times earlier reported on the ban.