Now that exchange-traded funds are all the rage,

Rydex

, a Bethesda, Md.-based fund company that courts market timers, has made it easier for trigger-happy investors to move among investments.

Its four

Dynamic Funds

, launched in May, began allowing intraday trading in July. The lineup comprises: the

Titan 500

, which aims to double the return of the

S&P 500 index on any given day; the

Tempest 500

, which attempts to return twice the inverse of the index (if the index falls 2%, for example, it aims to return 4%);

Velocity 100

, which tries to double the return of the

Nasdaq 100 index; and

Venture 100

, another Nasdaq 100 fund with a twice-the-inverse-return strategy. The funds are priced twice daily, at 10:30 a.m. and 3:45 p.m.

The many exchange-traded funds that have been recently introduced by

Barclay's Global Advisors

and others are priced and traded throughout the day. But all aim to simply match the performance of the index rather than double it.

Investors can move between the four Rydex Dynamic funds during the day, but they must first move into a money market fund if they want to trade between the Dynamic funds and other Rydex offerings.

For now, trades can only be placed by telephone or in writing, though Rydex promises that the funds will soon be tradable online.