Regulation play, sanctioned in the United States by the USA Ultimate, occurs at the college (open and women's divisions), club (open, women's, mixed + female on each team, masters, and grandmasters divisions) and youth levels (in boys and girls divisions), with annual championships in all divisions. Top teams from the championship series compete in semi-annual world championships regulated by the WFDF (alternating between Club Championships and National Championships), made up of national flying disc organizations and federations from about 50 countries.