Muller du Plessis, JC Pretorius and Sako Makata, who were part of South Africa's Commonwealth Games gold medal-winning sevens side earlier this year, have severed their connections with Sevens to pursue careers in the 15-man game.
Du Plessis, 23, who had played in 22 World Series tournaments since 2018, appeared in 102 games and shared in two World Series titles.
He is joining the Sharks, now coached by former Sevens mentor Neil Powell.
Pretorius, 24, has been one of the stars of South Africa's Sevens in recent years. He played in 23 series, scored 50 tries and played 122 games. He also shared in two World Series titles.
He was included in the World Rugby Series Dream Team in 2021 and has signed with the Lions.
Makata, 24, played in 17 World Series and scored 12 tries. He was involved in one of South Africa's World Sevens Series wins. He will play 15s for Griquas.