Eleven-year-old Muhammad is playing a game at his East Jakarta school that he earnestly explains is called "puti" (rhymes with footy).
Maulidan, a 10-year-old girl in a hijab, knows a little more: the principal, Pak Rizali, told them the game was from Australia. Both agree the ball looks funny. 
Asked if it is difficult to play, Maulidan replies: "A little bit, but we exercised for a week".
Sherrins might seem like misshapen balls in this soccer-crazed country, but Indonesian kids are naturals at Aussie Rules, according to Brenton Harris, president of the Jakarta Bintangs, an Australian Rules football club in Indonesia.
"They are outdoors a lot more than our kids," observes Mr Harris. "They are tenacious when they play - you should see the way they hammer each other."
For the past 10 years AFL Indonesia has been running free football clinics in schools and orphanages in Jakarta, Bogor, Bandung and Cileungsi. The code hopes to introduce young Indonesians to the iconic Australian sport. Already 51 per cent of the senior players in the three Indonesian clubs - the Jakarta Bintangs, Bali Geckos and Borneo Bears - are Indonesians. Boy Sabar Pasaribu started playing for the Bintangs nine years ago, when an Australian friend introduced him to the game. "I'd never seen it. I wanted to try a new sport - I said: 'No problem, I love it'."
Mr Pasaribu is now AFL Indonesia's first full-time development officer, whose role involves running Auskick clinics, providing schools and orphanages with sherrins and uniforms, and mentoring sports teachers to keep the game going.
Six months ago he gave a presentation to 75 schools in East Jakarta, with YouTube footage of Aussie Rules games, and invited four schools to sign up to the clinics.
"The next half hour they fought over who was going to be the four schools," Mr Harris says. "No other sport does it. Rugby is here but they don't seem to come to the kampungs (villages)."
Mr Pasaribu has a 12-year plan to hold regular Saturday footy games in Jakarta. But there are challenges - finding football fields, importing the sherrins and attracting sponsorship.
"We are hurting a bit with funding sponsorship because of expats leaving due to the downturn in the mining industry," Mr Harris says.
The program fits neatly with the Department of Foreign Affairs and Trade's new focus on sports diplomacy. The 2015-18 strategy launched in   June this year aims to use sports skills, facilities and knowledge to promote Australia and strengthen links with countries and communities in the region.
Health and Sport Minister Sussan Ley visited Muhammad and Maulidan's school as part of Australia's largest trade delegation to Indonesia last week.