Good questions.

Every pair is printed with a thermochromic (heat-reactive) pigment. Cool, each pair shows its first colour. Warm it up in the sun or in warm water and it shifts to the second: purple to blue, blue to green and orange to yellow, plus green to mint on Geometric. Cool water switches it back. See how it works

Look after them and they'll keep changing. Heat is what wears the effect down over time, so rinse in cool water, dry in the shade and skip hot washes, tumble dryers and the iron.

Men's shorts come in S to 3XL. Kids' sizes go by age, from 3 to 12. Check our size guide for every measurement, and if you're between sizes, size up. Not sure? Send us your waist measurement and we'll help you choose.

Both have the same thermochromic colour change, quick-dry four-way stretch, a mesh inner liner and a full elastic waist with drawcord, in S to 3XL. The Original is the bold, classic look. Geometric layers the colour change over a sharp triangle print, so it's a bit more subtle. See them side by side

Our kids' shorts are quick-dry with a full elastic waist and drawcord, in sizes for ages 3 to 12. They come in Purple to Blue, Orange to Yellow and Blue to Green, the same as dad's Original. Want both in one go? Grab a Dad & Mini set.

Orders leave us within 1–2 business days, and Australian orders are delivered within 6–10 business days of ordering. We'll email your tracking link as soon as your order ships, and you can track your order here.

We don't offer size swaps, so please check our size guide before you order. If the fit isn't right, tell us within 30 days of delivery and we'll send you a one-time code for 25% off your next order. It's part of our 30-Day Happiness Guarantee.

They're an easy one to get right. Not sure of their size? Go with their usual swim short size, or size up if they're between sizes. Kids' sizes go by age, so that's the easy part. Gift recipients are covered by our 30-Day Happiness Guarantee too.