NEW YORK (AP) — The boxing battles among Sugar Ray Leonard, Marvelous Marvin Hagler, Thomas Hearns and Roberto Duran will be chronicled in an upcoming four-part documentary.

Showtime will air “The Kings” beginning June 6. It focuses on the four Hall of Fame fighters who met a combined nine times in the 1980s and provided some of the most memorable matchups of their era.

The series of fights started with Duran’s victory over Leonard in their first bout in 1980 and culminated with Leonard’s draw against Hearns in their second fight in 1989.

It included Hagler’s knockout of Hearns in their 1985 brawl that included an epic first round considered one of the best in boxing history, and Leonard’s disputed victory over Hagler in the longtime middleweight champion’s final fight in 1987.

Three of the bouts were recognized by The Ring magazine as its “Fight of the Year.”

Showtime Sports President Stephen Espinoza said the four fighters “defined an era in boxing,” renewing popularity in the sport following the retirement of Muhammad Ali.

All episodes of the weekly series will be available across Showtime’s on-demand and streaming platforms.