Each Mavi Bandz comes with an adjustable back - making it a perfect fit every time. These fit most 4 years old and up. Each Mavi Band has our high quality, non-slip technology on the inside to ensure it stays in place all day! Every Mavi Band comes with a lifetime guarantee of happiness! These headbands are perfect for working out, running, soccer, basketball, volleyball, softball, pilates, barre, yoga, marathons, races, gymnastics, dance, cheer, or just going out with friends! This is the perfect hair accessory for every occasion!