What's the most important thing when buying a kids helmet?

Across both expert testers and community threads, fit is the consistent theme. Reviewers on r/australia and r/CargoBike repeat that 'the helmet that fits best is the best,' and that a correctly fitted budget helmet outperforms a poorly fitted premium one. Look for a dial retention system, adjustable straps, and a size range matched to your child's measured head circumference rather than just an age label.