Think of unicycles and it might well be a circus that comes to mind.
But teenager Sam Verebes takes his one-wheeled bicycle very seriously.
The West Island School pupil will today balance atop a 71cm wheel and pedal 42 kilometres through Plover Cove Country Park for charity.
When he completes the route from Tai Wai MTR station along a path across the reservoir at Tai Mei Tuk, Sam will have completed his 13th unicycle marathon in six months, one for every year of his life.
Watch: Hong Kong Jewish boy marks bar mitzvah birthday with unicycle marathon for charity
He expects the ride to take 4-1/2 hours at an average speed of 15km/h - which may not sound fast, until you consider that the bike has no brakes.
"It's definitely going to be hard, but I'll manage," he says, adding: "I like a bit of danger."
Sam, who first rode a unicycle just 18 months ago, is raising money for Roll Out the Barrel, a charity that makes it easier for children in poor countries to collect water for their families.
He decided to take up the challenge to mark his bar mitzvah, the coming-of-age ritual Jewish boys celebrate on their 13th birthday.
"Most bar mitzvah boys do some sort of charity project, so I decided I wanted to do something extreme with my unicycle. At first I thought 130 kilometres would be good, but then I managed to do that in a month," Sam explains.
He has already completed 504 kilometres and raised HK$23,000 from his page on the Just Giving fund-raising website.
His donations so far have helped 65 families by providing them with HK$350 barrels.
"Instead of kids carrying huge buckets on their heads - which is bad for their backs and necks having to carry it kilometres before school every morning - these barrels come with a handle and can be rolled," Sam said. "It's easier for them to pull along and it definitely improves their lives."
The Briton, who moved to Hong Kong with his family five years ago, took inspiration from a book featuring a "cool" unicycle rider "and there was a picture of him up a mountain… so I thought I'd like to try it".
But Sam soon discovered it wasn't as easy as it looked.
"At first it was really hard. I could barely do a pedal," he recalls. "I bashed up my toes and ankle. Now it's just as easy as riding a bike. I don't even have to think about it."
He has since conquered some of Hong Kong's most rugged territory, including The Peak.
There have been a few close shaves.
"A few times the unicycle has almost slipped straight off The Peak," Sam says "But there's been a barrier, and I caught the handle just in time."
Sam says his parents didn't quite know what to make of their son's big idea. "They didn't actually think I was going to try it but they're very supportive and I've proved them wrong."