The Giro Launch is the gold standard for little kids helmets. Available in many colors and a low profile fit it's a go to for that toddler that needs their first dome shield. 

Helmets are measured in center meters around the crown of the head.

Giro Sizes:

X - Small : 48.5 cm - 52 cm

Small : 52 cm - 55 cm

Giro Launch Jr