Australian heartthrobs 5 Seconds Of Summer are having a great career so far and they have now been praised by one of their co-writers for being so great to work with.

29-year-old Jake Sinclair recently told People magazine that he wrote 'She Looks So Perfect' after he had been buying boxer briefs at the store mentioned in the song:

"I came up with it when I was in line buying underwear at American Apparel. And then I was like, 'That'll be perfect for these kids!' We finished writing it and produced it that day."

Sinclair went onto add: "They're really positive and fun to have in the studio... It was really easy." 

All Time Low's Alex Gaskarth also weighed in on the lads' professionalism and dynamic as a pop-punk quartet, and admitted that they're really close and work so well together:

"They have a very similar dynamic to our band: Everybody gets along. To see another group doing it a few years younger than us – it's really cool. Songwriting's a good time. We weren't taking ourselves too seriously ... If you're not laughing and having fun doing it, you're doing it wrong."

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Watch a new interview with 5SOS below: