According to PANews, the fee rate for the Grayscale Mini version GBTC 'Bitcoin Mini Trust' could be 0.15%. This information was shared by Bloomberg ETF analyst Eric Balchunas on Twitter. He clarified that this is an estimated figure and is therefore hypothetical, meaning it could change before being officially released. If the 'Bitcoin Mini Trust' fee rate is indeed 0.15%, it would be the cheapest BTC ETF currently available in the market.