The lucky 300 who got their hands on the burger (Photo by Xavier Teo) More

All sold out in just five minutes.

American burger joint In-N-Out's first pop-up store at Circular Road sparked a mad rush by over 300 curious Singaporeans as well as hardcore burger fans on Tuesday morning.

The queue at Golden Grill restaurant, which In-N-Out specially chose to hold its guerilla-style promotion, started forming at 9.30am and went all the way through Circular Road out to Boat Quay.

Wristbands which entitled each customer to claim one burger were handed out shortly before 11am. In five minutes, all 300 or so wristbands were given out.

Its specialty, the Double-Double, went for S$6, while cheeseburgers and hamburgers went for S$5 and S$4 respectively.

In-N-Out's famous Double-Double. (Photo by Xavier Teo) More

American Xavier Teo, 32, a big fan of the US burger chain, was among those lucky enough to be in the queue.

The business development manager told Yahoo! Singapore that their famous burgers, well known for its fresh and quality produce, lived up to its reputation.

"I would say the taste was 80 per cent of how it is back in the States... but it's still better than the burger joints in Singapore. They kinda skimped on the goods, and the patties were a little smaller but it was still worth the 1-and-a-half-hour wait," he said.

"There were a lot of Americans there and some curious locals in the queue... They passed out the wristbands at around 1045 and told us one wristband equals to one burger, which was a little disappointing, " he said.

"Overall, it was a great experience. Going to In-N-Outs is a Californian tradition, much like chicken rice in Singapore," Teo added.

In-N-Out's guerilla-style, pop-up store at Circular Road. (http://lesterchan.net/) More

Others, however, were not so lucky.

Singaporean Lester Chan, 28, arrived just after 11am and realised the burgers had sold out as the crowd was slowly beginning to disperse.

"The place was mildly crowded surrounding the store. I saw many people got off the taxi just for it, but saw the disappointment on their faces when they were told it is sold out."

Tuesday's pop-up store was a test case for In-N-Out -- a family-run chain famous in the US West Coast -- to see if it's worth setting up a permanent store in Singapore.

Well, looks like they have their answer now.