Shares of the Valkyrie Bitcoin Strategy exchange-traded fund /zigman2/quotes/230473388/composite BTF -0.72% were trading flat to lower on Friday as the U.S's second ETF linked to bitcoin /zigman2/quotes/31322028/realtime BTCUSD -0.96% made its debut on Wall Street. The launch of the Valkyrie Bitcoin fund comes days after the ProShares Bitcoin Strategy ETF /zigman2/quotes/230440344/composite BITO -0.44% became the first U.S. ETF linked to bitcoin on Tuesday, in a watershed moment for the crypto sector. Both Valkyrie and ProShares's funds are futures based, which Gary Gensler, chairman of the Securities and Exchange Commission has said provides better protections for individual investors. Gensler's statements about futures-pegged bitcoin ETFs, made in the summer have paved to way for fund providers to propose a parade of futures-linnked products. Futures are derivative financial contracts that provide investors exposure to price moves in an underlying asset. However, the value of futures contracts sometimes diverge from the underlying asset, which is one of a number of criticisms of a bitcoin futures ETF. The ProShares ETF were up 0.7% early Friday, however. Both Valkyrie and ProShares carry expense ratios of 0.95%, which means that investors annually pay $9.50 for every $1,000 invested in the fund.