After-hours data shows that on October 21, a total of 34 stocks appeared on the leaderboard with institutional involvement, with 14 stocks showing net purchases by institutions and 20 stocks showing net sales. The top three stocks with the highest net purchases by institutions that day were Arcplus, ONLINE OFFLINE, and DYEC, with net purchase amounts of 1.051 billion yuan, 142 million yuan, and 87.36 million yuan, respectively. The top three stocks with the highest net sales by institutions that day were Yuanjie Technology, Huilv Ecology, and Yunhan Xincheng, with net outflow amounts of 263 million yuan, 157 million yuan, and 112 million yuan, respectively